I would like some help with this game.  As far as I can tell, I did pretty good up until move 16.  Any help would be appreciated.

I didn't particulary like 12. ... c5 because it gives up the flexibility of your pawn structure. You want to be able to play ... d5 and/or ... e5.

 

I don't like 13. ... e5. This will leave you with a backwards pawn on d6 that white will be able to attack easily. You will spend too much effort defending it. If your pawn were still on c6 and you had the option of playing ... d5 this would be a different story.

 

You might be fine after 15. ... Be6 intending to exchange for the knight. Then your bishop on e5 is immovable and you can probably hold that structure, though I don't see any attacking possibilities, so you are probably playing for a draw.

 

15. ... Ba6 just loses a piece.

 

After you are down a piece you need to play more aggressively. 18. ... Rbd8 19. Qxc5 Rb2. Getting a rook on your opponent's second rank leads to attacking possibilities. Then you can double you rooks on the d-file. Since your opponent has more pieces, he should be able to defend, but you have to at least make it difficult.