Inner West Swiss - Round 2

In this game I'm facing the King's Gambit and my opponent has a FIDE rating of 1746. Having never learned the accepted lines, I answer with 2...Bc5, the KGD classical defence. For some reason I decide to castle queenside(?!) and quickly find myself under immense pressure from his queenside and central pawns. I even manage to win a pawn in the middlegame (and decline the option of a second?!) but can't see a way to convert this in the resulting rook + pawn endgame. How frustrating.