Why is my rating so low

You're right about the exchange. Something to keep in mind in the future. I've lost a few games where I was winning and I refused to exchange queens.

I noticed all the games I've played I win the center but then suddenly they're a move or two from checkmate and I'm just constantly defending until I lost. I don't know how to avoid this. It seems like a big part of my issue is not knowing how to go about getting checkmate in most situations.

After 1 e4 d5, the usual move is 2 exd5.

I'm about to just quit. I don't understand how I was getting close to 1000 and over a few days I'm down to 750. I've played 2000 games and only gotten worse. This is unbelievable and it's not fun anymore.

If your games are primarily G/10, I'd strongly suggest adding in games with longer time controls.  By only playing blitz and rapid games, you aren't building a good foundation on which to improve as a player.  I feel it is easier to develop good habits playing the slower time controls rather than handicapping yourself by only playing quick chess.

Utilize a database to go over games of openings you are thinking about playing.  At the lower levels, chess is all about pattern recognition.  If you start to go over higher quality games, you will have a better idea of how to play the opening (Where pieces are typically placed and typical patterns of development).

"He had given no indication at this point that he was a good enough player to see a revealed check double-attack so I wasn't looking for it."

When playing chess, remember that assumption is the mother of all... mistakes.  Never assume that a move must be made or limit your search for candidate moves because you think that an opponent won't be able to find it.  Always search for the best move possible. 

I wouldn't get too discouraged about your rating.  You may very well be improving and on the verge of a big rating increase.

I hope that you don't decide to quit and are able to accomplish the improvement that you seek.

I sent you a friend request and a challenge for an unrated daily game.  I set it for game in 7 days to allow the most time possible but I don't typically move that slow.

"..., you have to make a decision: have tons of fun playing blitz (without learning much), or be serious and play with longer time controls so you can actually think.

One isn't better than another. Having fun playing bullet is great stuff, while 3-0 and 5-0 are also ways to get your pulse pounding and blood pressure leaping off the charts. But will you become a good player? Most likely not.

Of course, you can do both (long and fast games), ..." - IM Jeremy Silman (June 9, 2016)

https://www.chess.com/article/view/longer-time-controls-are-more-instructive

Maybe you start to get stressed because you are up and you feel like you have ot prove something. Try not to dominate. The exchange would have made the difference, you could have the proceeded with moving your bishop and then castle. Black would have no positional advantage to compensate for the last rook and you could just trade him down. Don't worry about having the coolest checkmate, especially in a blitz like this you will stress on time. 

I had a few good games after this post, I'm feeling a bit better about it lol. There does seem to be a delayed improvement that comes from studying tactics.

Your first game: 2. Bd3 was a mistake. You lost time with the bishop.

The second game, Qe5+ is a mistake. What do you achieve with this? Be2 blocks the check and look at the development. 2 minor pieces out and Nf3 can kick the queen, losing even more tempo

From your first post there, some of those tactics were quite nice for a 700-rated opponent to find, like 15...Nxc2, removing the defender. It's important to remember that low-rated players aren't stupid - many of them know a lot about how tactics work. What they struggle with is consistency. Become more consistent than them (at not blundering and at exploiting their blunders) and you'll rise through the ranks!

I'd be happy to keep in touch and even look at an annotated (= share your thoughts for each move you played, so I can see what I can identify and fix in your thought process) game you played! I'm actually working on a new project to help chess players improve - all free. Feel free to check out my site at chesspathways.com - I'd like to hear from you. You can get past this phase in your chess development!

@PolarPheonix I'm confused by your commentary since I don't know which game is which. I believe in the second one I'm playing black and won easily. Unfortunately since I don't know which pieces I'm playing and I can't quite understand you it's not really helpful.

Btw after just a few games on lichess I'm rated around 1300 and consistently win/draw around that rating. I think there is something fishy going on here, although obviously I need to improve anyways.

@BlakeyBChess I thought I was past this stage which is what makes it so frustrating. I was rated 975 when my lowest was 650. I was consistently winning and suddenly I'm consistently losing. I'm still studying tactics and trying to improve and look at my games, but my rating just keeps plummeting.

You should stop playing blitz games,play rapid 15|10 and not more than 5 games a day.Most of the time you should spend studying tactics on chess tempo and rest on studying master games.Do this and i am sure you will be rated above 1000 very little time.Most important till 1000 rating is to not blunder and not fall prey to 1 or 2 move tactics.

Focus on playing quality games over a greater quantity of games.  While the 10 minute games are convenient for online play, they aren't helping you improve your play. Playing games with a longer time control and using that extra time wisely will help you avoid simple mistakes.

Go over games that you play.  Use a chess engine to point out the mistakes you've made.  Also don't be afraid to share games with others to help show you the mistakes that might not be so obvious.  Other players can explain why a plan or a strategy might be bad.

You need to stop focusing so much on your rating as the definitive indicator of how strong you are as a player.  By focusing only on wins and losses, you overlook improvements that you need to make and improvements that you are making as a player.

Hey, maybe you should start focusing on improving your chess instead of playing.

Watch videos on pawn structures and basic endgames, and do a ton of tactics. (atleast 20-30 a day) and you will rise with no rpoblem over the next month.

Dude, do more tactics.  When you do tactics, calculate the entire line before doing the first move.  I noticed you said you wanted to quit in another comment due to not improving, I had two friends who were about your level and quit because of no improvement.  I recommended tactics training multiple times and they never listened, really all you need to do is TACTICS!

@Mark_Zambelli this is the first game I played after doing some tactics training. Perhaps it is the key lol. You see the board in a totally different way. I have no idea why he resigned so early, only being down a rook though.

lichess has unlimited tactics btw.

@Mark_Zambelli this is my second game after doing tactics lol. Suddenly chess is fun again. I think this really is where I need to focus.