Different points for wins and losses? Checkmate recorded as loss?

When I first joined Chess.com a month ago the system was win or lose 8 points flat. Now when I lose, I'm losing anywhere from 9 to 15 points and when I win only getting between 1 and 5 points. What is going on? I'm playing the same 20-minute standard games. This is really hurting my rating unfairly because I'm losing more points than I can win this way. I also just won a game by checkmate before the clock ran out and despite the game report analysis showing my last move as checkmate, I didn't get the win and was given a loss of 15 points. Now the friend I beat is making fun of me, lol. Come on can this be fixed? I'm a platinum subscriber so I'm not sure whether that makes a difference.

The rating system isn't static.  How many points are awarded or taken away depends on a rather complex formula devised by one Professor Glicko.  Let me run and get the article for you...

Here you go

https://support.chess.com/article/210-how-do-ratings-work-on-chess-com

Your second question?  Just because your computer shows a move as having been made unfortunately doesn't mean it made it to the servers in time.  You aren't on iOS, are you?  The last two versions have had some major problems.  Otherwise you probably just had a temporary disconnect...Why yes, I am going to run off and get you the article,,,

https://support.chess.com/article/213-how-do-i-fix-my-disconnect-lag-issues