I'd say your biggest mistakes are 14. f4 to 17. Bd2 where you progressively tuck away your most active piece, the dark bishop. Black could have had a much stronger attack down the queen-side if not for diving in head-first with the queen. 14. Bd4 would help to secure your queen-side and allow you to develop your knight.
a3 and h3 aren't really mistakes, they are good precautions to take, much like h6 would have been a good precaution for black to avoid the back-rank mate. Eventually you should be able to prevent the bishop-knight combos without these defences.
The following is a game I played as white, please provide your feedback...note, I know the opening is unconventional, that's intentional.