Is This a Fortress?

In an over-the-board game last night, I reached the following position, playing Black:

I've spent the last dozen moves mostly toggling my king between c5 and b4, while my opponent  tried ot find a way through on the kingside. Does Black have a fortress here, or can White break through?  I have a strong suspicion White can win this, though it's not as clear as I'd thought.  After 41... Kc5 42. Kh4 Rf5 43. g4, there's 43. ... Bf6+ 44. Kh3 hxg4+ 45. Kxg4 Rg5+ 46. Kf4, and maybe Black can somehow reconvene in a new configuration that holds.

At this point, when we were the last game in the room and both getting weary, I spotted what I thought was a nifty swindle and played 41 ... Rxg3+, with the idea of giving up a bishop and rook for a bishop and pawn, so that my king can sneak in.  White, I figured, has to give up the other rook for the d-pawn, and then I win the queenside pawns and the game.  Of course, a silicon reality check reveals that the sacrifice is incorrect.  After the trades on g3, White can drop the rook back to e7, where it has just enough time to win the b-pawn before giving itself up for the d-pawn, after which White's c-pawn wins.  But at 10:30 at night and without much time on the clock, we both missed this.  After an hour of slow, careful manouvering, this move came with enough shock that my opponent (a really nice guy), crumpled, and I won a game I thought was hopeless.

So back to the quesiton of whether it's a fortress.  Did I swindle a win out of a lost position?  Or did I blunder in a drawn position?

After 41...Kc5 why not 42.Rf3

Could be.  I probably play Kb4 again there.  What's your idea for breaking through? 

Congrats on the win. I don't think it's a fortress but I do believe you have good drawing chances.

I suspect white wins with something like Rf2-f7-h7 and Kh4 picking up the h-pawn.

What's your plan against, say, Kh4 with g4? I'll exchange the pawn, my king is free to move, I have all kingside open for my rooks. No way in hell is black holding this.

White should win this. 1...Kc5 2 Rf3 Kb4 3 Re4 Kc5 4 Kh4

Thanks, all.  My hunch was it was losing, so I feel a little better about trying a tricky line that I couldn't fully calculate.  Still, I should have found White's win there.

I don't exactly think it's a fortress since White can penetrate the fortress in 3 moves. White will lose a rook, but the fortress is penetrated, so I don't think that this position is a fortress at all.

I was looking at .. Kc5, Rf2 Kb4, Rff3 Kc5, Kh4 and the h Pawn falls.  Once you have the extra Pawn (after Kxh5)  then you can play Kh4, Rf7, Rd7 and Rd5.