When my opponent started with the kingside pawn advance I originally thought that it was not sound but then I saw that I had some problems to solve and it was not so easy to handle but I do not think that I got overly worried at all.

Well i didn't analyze the game with the computer to figure out what would of been "Ideal".  I am interested here in more towards what your thought process was when he did his pawn push right after you castled. 

What were you thinking(omg he's getting me, or oh crap etc..)?

I believe here the psychology of the moment might of been a factor.

Also i took another look and move 13 you moved your knight backwards (Cramping you) why not stick it ontop of your pawn structure in the middle of the board .  If he trades he trades and your less cramped...From my understanding this is the IDEAL thing to do with tactics in mind.

Yes, thanks. I actually think castling was not the problem. I think I played a couple of second and third best moves once white played the kingside pawn advances which led me to having a worse position.

Only thing i see is that you castled prematurely, i am not up to your skill level but it just seems to me that you castled to early and gave him the chance for a big initiative.