When was your position better, exactly ? (you are at some point, but do you know where ?)
White is behind in material at some times, but he still has the initiative.
3...f6 (?) isn't great, and 5...c4 ? worsens it. If you want to play the French, look it up a bit, or you will just have locked you bishop c8 for nothing.
11...g5 ? does not even win a piece after 12.Ng6, so it is a bad idea to play it. 11...0-0-0 instead, and even if 12.Ng6 Rh7 is not a pleasant road to walk, Black is playing.
Move 14 sacrifices a piece for not much, so you are better after that.
18...Qxb2 ? : instead of hunting for more material, you should prepare the defense. One more piece is more than enough to win an endgame, but you need to reach it alive ! Had White found 20.e6 Bg6 21.f4, with the idea 21...g5 f5, you would have been in serious trouble.
26...Bg6 ?? : the losing move. You must keep the f file closed at all costs, which means ...g4. After that, 27...Kg8 28.Qxe7 Rh7 survives a little longer, but the e and d pawns will be too hard to stop (because of the misplaced greedy queen, among other things).
I slipped in a better position :P