I tied myself up here - how?

A recent game. I won this after a blunder, but I was somehow tying myself in knots despite a clearly superior position. I was frankly, out of a plan. From move 19, I wasn't really sure what I was doing, and how best to make use of my position. Any thoughts/comments?

Thanks! 

white looks like they are having a really bad day or they have a largely inflated rating in my honest opinion.

These aren't chess.com ratings, but yes it was a weak game for white..

It's a difficult position for Black to play.  Your pawns are compromised on both sides, which makes it tough to make progress.

You were doing a good job of it though.  Even without the blunder, you're ready to simplify either with Bb5 or the idea 27... c5 28 bc b5.

I would have been tempted to play ... c5 on move 19. After all, White can hardly answer 20. b5 axb5 21. Nxb5 Bd3+

yeah, that looks good

Just seems like one of those dreaded bad games. White had no clue what they were doing and the position after 27 was obviously in blacks favor.