The blunder was in your move 37. You lost the potential advantage here. 37.Rf8+ clearly had a mating potential. With the pawn capture move you lost the initiative to black. Even 37.c3 was much better than what you played.
Was there a mate?
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Wait! I was wrong. Black did not respond correctly to your 37th move error and instead carried on with a bigger blunder Qd2. The REAL blunder was with your move 42. Wrong place to check him at ...
Also, you missed a mate opportunity at your move 74. You got to look at this deadly knight check at move 74. I think you were trying to look for a threefold repitition here which you didn't get. If you had played this knight move ...
A little variation here. If black responds to 74.Nb6+ with 74...Kc7 then 75.Qxe5+ Kxb6 76.Kd4+ and queens are exchanged.
I think the critical position is at move 40. Clearly you have an attack, but it isn't trivial to find a mate. Here's my heuristic on why this is so:
Mate exists: Black's king is isolated and horribly exposed. You have a powerful queen/bishop combination. Black's king is cornered.
Mate doesn't exist: Black is threatening a (visually) unstoppable mate in 1 if given a single tempo. White's bishop is blocking up the f file for white's Re1. White's knight looks useless.
That enables us to focus our search for the right move sequence.
Heuristic 1: Every move must be a check.
Heuristic 2: If the bishop moves away from f5, black's king is cut off from the f-file, since enabling Rf1+ is suicidal for black.
So one method of finding mate is to chase black's king to the queenside, where white's knight will (hopefully) find a place in the all-out king attack, while another is to keep black's king on the kingside and move the bishop away from the f-file.
Some sample lines (warning: I was just dragging pieces most of the time)
I ended up losing this game on time searching for mate.
Was there a mate somewhere?