The pawns could have gotten to the other side
Practical Queen Ending
Care to elaborate? I mean, that's like saying "You could have played better" - the question is how? Something more concrete

Typically in queen endings, material doesn't matter nearly as much and the person who has the furthest advanced passed pawn will likely win.

I think you were close to winning after 27. ... qd6 instead of 27. ... fxe6, with the idea of 28. qe3 kf8. As played, you allowed the white queen to cut off your king, and in general a queen is not sufficient to stop a passed pawn supported by an enemy queen without support, as you found out in the game.

I agree with Killabeez. The passed pawn is key in queen endings. So 25. ... Qc1+ wins a pawn but allows your opponent to create a passed pawn. After that, you're probably lost.
You give 29. ... a5 a "?" for not protecting the d-pawn, but how would you protect it?
29. ... Qd6 30. Qf7+ Kh8 31. e7 and you're in big trouble.
29. ... Qb7 30. Qg5 continues to threaten the d-pawn and now threatens Qd8#
This is a game of blitz I played (and lost) as black earlier tonight. The opening and middlegame could use some analysis, but I'm posting it here because I think the heart of the game was the queen ending. Any analysis and suggestions would be appreciated.