Ouch! My brain hurts!

My latest completed game at chess.com really made my brain hurt.  I played the Tarrasch defence to the Queen's Gambit and won a pawn on move 20 due to an oversight by my opponent.

Despite this good start, I felt on edge for the whole game and was relieved to eventually get the win.  The game is below with my comments.  Constructive criticism of my play is welcome!