Preparing ...f5 perhaps. But I prefer 11...Nxe3 followed by ...0-0 here.

This move was interesting instead of Be7, not now, just because of your next's one.

That's good. Now, this move also implies you have to be careful about the future of this B. If Rg8, black can trap it with g4 and then take it. This or something like this should be an any-move-concern from now on. You get something but it always costs you something else...

Chess consist in looking at where the pieces can go. This move was possible even before, and you weren't aware of it...

14...Nb4 would have been very nasty.

Indeed. If Qc4, d5! and the Q can't take the N because of QxNb4, Nd3+ and fork. Black's developement would have shown his power.

Three pawns for the knight. But Black has a very powerful centre. I think I'd rather have the pawns.

You had sound mistkes from your opponent... and still you are the weak side (just look the board from a distance: black has to reasset himself, but white has... nothing, just border pieces).

Oops...

Black could have done far better than this by playing 16...d4! This discovers an attack on the h1-rook, and threatens a fork by 17...d3. You should never pass up tactical shots like this!

Yes. And on second choice, e4, supporting Nd3 was also very good for black.

16...e4 is pretty bad for black, 17. O-O makes Nd3 useless and the LSB is blocked from his diagonal.

Reasonable, but I still like 17...d4, with moves like ...d3 and ...Qd5 in mind.

Good move.

Can you go back into the game and see where and when this move could have (or not) played before. Despite the nasty white's square's alignement, it was always to be taken into consideration. Once black castled queenside, this B should have come back to help with white's "attack" (Be3 threats a7).