I WAS SHOCKED WHEN MY OPPONENT PLAYED THIS CHESS MOVE!!

I hope you don't mind the criticism: If you don't want to play too passively, why didn't you develop the bishop on the h3 c8 diagonal before closing the pawn chain with e6; the d4 pawn looks fixed and you no longer have a c pawn to challenge it and the e4 square is defended very well, so the bishop on b7 is very poorly placed. Queen b3 is never a real threat if you know how to handle it. After that, you practically never managed to move the white-squared bishop, which is why you never were able to move the rook on a8. Hence, you played half the game without two pieces and after h4, maybe g5 was the way to go but that's probably my bullet intuition. Also, the rating is irrelevant. I think that's very important to point out, especially to an intermediate audience. Your opponent blitzed out moves, so the game wasn't that educational – at least for him. Maybe you could include daily position studies. As many grandmasters and coaches pointed out, you should also never use an engine to analyze unless you are at a master level. 

I have no problem with criticism, pretty much all the lines with developing the bishop before e3 lose a pawn. Me not developing my bishop was due to my inexperience in the opening but you can develop the bishop by pushing e5 and opening up the position. 

@OttoMesiter in the exchange slav defense, b6 is obviously almost never a possibility, because a6 is usually a necessity (anything coming to b5; b6 would be a backwards pawn), and b5 gives up the dark-squared color complex on the queenside. Therefore, in the exchange slav defense, the bishop is always developed to d7 if the pawn chain is closed early; from there bishop "sometimes" (in rare cases approved by the engine) moves to c6 in order to make it more active. In particular, with bishop f4 on the board, e5 is almost never a good plan in the exchange slav defense, because white has this square so well under control and black usually never gets the time to push it successfully. Therefore e5 would be a tactical possibility here, if at all, and not a practical plan. Opening rules are to be followed in any opening, and developing a piece is almost never a bad move. You never developed your entire queenside: The rook and bishop came into play much too late. If you don't have a thorough understanding of the opening, then you need to superimpose your general understanding of chess and stick to principles, which would have led you to the correct handling of the position. Also: Before you develop your bishop on the mentioned diagonal, knight c6 is of course a requirement because of the resource knight a5. Only then can the pawn chain be closed, but even this move you would have found with general opening principles. If the bishop is not on b7 and then you open the position with e5 which costs a lot of time (you move the e-pawn twice; you will probably have to move the bishop twice; you have to prepare e5 with some moves that most likely won't be developing moves), then simultaneously you rely on the resource e5 which can also become impossible if white knows how to prevent e5, which is not implausible – at least temporary. In any case, as long as e5 is not available, you play without two pieces, and that on the queenside, which is dire because a large portion of the middlegame will take place on the queenside.

Anyway, I don't understand why you play the slav defense unless you are a theory fanatic. The benoni is at least fun like the volga and you learn to attack and calculate. Play sharper lines.