Where did I go wrong?

Here is a game I played a while ago. I know I blundered a lot at the end, but what other bad moves did I happen to make? Thanks guys!

Here's the game:

3. c4! - punish weak moves with play in the center!

your note to your 4th move is puzzling - the pawn chain is actually not that puzzling. you can nibble at the tip with h4 at any point and the fact that his pawns have advanced only weakens his light squares.

I don't think 7. g3 is correct because your light bishop really belongs on d3, or at least the b1 - h7 diagonal. Black opened up this diagonal just for you, so take it!

14. e4!? is interesting

18. Qxb6 axb6 19. Rxd7 and Black is toast (and that's a bad thing!)

sick game! I can tell you have a lot of courage - just keep improving and it'll pay off. Remember that fortune favors the brave.

A few comments

Losing a tempo with 3.Bf4 isn't so bad given that he's torpedo-ing  his king safety right out of the opening.

4.Nxg5 is hasty. Never sacrifice material unless you have a tactical reason or some positional compensation at the end.  When you are down material with nothing to show for it, you are LOSING...there's no arguing around that.

Get your pieces out, mobilize them on that weak f7-h5 diagonal and then go in for a kill-shot.

Your rationale here that his "pawn chain is too strong" is not accurate. He leaves potentially terrible white square holes and exposes his uncastled king, not to mention leaves his pieces underdeveloped.   You have to learn to weigh one factor vs. others. In this case, the "strong chain" is insignificant vs. the weaknesses he creates.

 7.g3 seems to ignore  the key weakness for black here.  You want to move the e pawn and get your queen on h5 ASAP before he can try to cover his exposed king.

13.O-O-O. When you are winning, avoid castling on opposite sides as you tend to give him more chances to create complications.

14.Rhf1 : Loses a pawn for nothing. Even the passive Rdf1 is better. If you want to survive against stronger players, you have to STOP dropping pawns and thinking you can compensate for them later. At the level you're at, material is material. period.

In this position, why panic about the fork when you can pin his knight to the king with your rooks? I'd rather play something like Bg5 and dare him to take on f2.

16. Rxd5.  I agree, Bxd5 looks way better. 

18. Qg5 : As you pointed out, this mistake ends things for you.  As a general piece of advice, always dedicate some time to answering the question "What is my opponent trying to do with his last move?".

Overall, a game with a lot of potential for you to murder black quickly ... but you have to play tactically safe moves even when you are attacking.

Haha yeah guys I think I missed a lot. Well thanks for pointing them out, I'lll definitely give your suggestions a try (especially the one about dropping material...)

Very useful and sound advice Shuttlecnase 92, and Shivsky, very sound advice indeed!

Jeez looking back on this game it seems as if my play is really bad LOL