- It took forever to get my knight into the game.
- It took me too long to castle
- I felt stuck in the back.
Help with my middle game thinking.

Just looking at the position at move 8, it appears that black has a real edge, but you just sort of played your rating, making a bunch of not best moves such that you gradually lost the edge, and things look roughly equal before your move 20. My approach is not to analyze whole games - too lazy for that, sorry - but to pick a spot or two where I think I can teach something. So I'd like to focus on your 20th move. By trading rooks, you cede the open cfile to white, and qc7 (the only way I'm seeing to challenge for the file) at best spends a move and moves the queen to a less active square. Whether this gives white a real edge isn't really the point - rather, you should see that the move gives white control of the open file, and reject it absent additional factors. Sometimes an open file cant be used, or one's own remaining rook can deploy on another open file or half-open file. Here, the trade gives white's remaining rook something useful to do (at a minimum), while your remaining rook is doing nothing - with improvement, this sort of trade will come to seem visually wrong.
6. ... cxd4 is inaccurate. That allows white to develop his queenside knight to c3 instead of the inferior d2. Instead wait with the capture, and put more pressure on d4. Moves like Nc6, Qb6 and the manouver Bg6-Ne7-Nf5 before developing dark square bishop to e7.
Having a point to pressure is good, because you can develop your pieces with a plan.
20. ... Rxc1 is bad. Almost deserving of a questionmark. By that trade you give the only open file to white! After that you are pacified by white's pieces - the c-file included.
The battle for open files is often a staring contest. Whoever captures, loses the file.
Retreating your queen to b8, for a stupid threat, is also bad. It blocks in your rook. Don't threat for the sake of threatening. Consider if the threat improves your pieces, and only if the threat does, then perform the threat. Putting your queen on b8 only worsened your position.
Don't let the fact that you won make you think you played well. Sometimes you win after awful chess, and sometimes you lose despite playing a very good game.