Most complex position so far...

I'm fairly new to chess, starting off with blitz but then went up to standard and recently on-line. This position perplexed me so much I must have spent at least 3 hours just looking at this one move - and obviously where it led me! It was against iMensan online (I struggled with the full PGN format) He was rated about 1400, me similar but only because of a lucky run in my first 4 online games

So I'd be interested in what is the strongest move and why

I was previously very close losing with his knight checking me and my pawn pinned by the Queen. I was aware he could do the same with his pawn and queen

I was trying to promote my pawn, but obviously ties up with his rooks, though it kept his rooks busy for now. Material was even at this stage

Thanks for having a look.

Captain Caveman

Full game is here and this position came from move 27 http://www.chess.com/echess/game?id=62445432

White's previous move, 27. Nf4, was a blunder. He should have played 27. fxg6 for an easy win.

The correct way to capitalize on this mistake is 27... Nxf4 28. Qxf4, after which black can win a pawn with either Qxb2 or Qxd3.