I have very strange problem about sex, All the guys-do see and give opinion .. thus help me. Options

[anay]

My very first post in this forum.
I am 19 and for my badluck I am still virgin. I have been with few girls but never got chance to have complete sex though had lot of fun like foreplay. I am also regular to gym from a year and more and have a strong build physic by now.

So case is that i decided to remove virginity and went to prostitude with my friend. (my friend is experienced stuff in such thing).
So basically girl there was fine but place was messy.. no privacy, a big room dividing by curtais in part and in betwee people are coming to check if this one is empty etc. So what bad happened is that.. I was with girl for half hour and there was not even erection in my d**k :( .. that was so much harrasment for me. She tried hard to turn me on.. but I was all cool . Even she was all naked in front of me.. caresing me but i was not getting on heat .. I was not hving any sensation at all.

Well.. after hlf hr .. I had to leave (wasted money though) and i was out without doing anything with insult also.

Basically I have my exam to be started next day so I think I was in little tension and more over there was no privacy at all. I came to home and try to erect in bathroom and it was all fine in 3-4 minz.. and whenver I think of that situation .. it was again going down.

Guys.. kindly give me ur views that what happend with.. I m really not fine after that incidence..
Is that I got Immune to girls?
A day befre that I was with my girlfriend (we don't do compelete sex ) and I was realy turned on with her.. :(