Ok, this is rather random and I am going to phone the GP first thing monday to get an appointment anyways but, recently I got with a girl I really like (im 18) Ive had relationships before and Sex and its all been great. However me and this new girl were fooling about in mine and I had an erection and all that then we went to have sex and it disappeared (which is strange because i actually feel comfortable with her) she was really cool about it so I just thought to myself its a one time thing, anyways same thing happened in the morning when we tryed it again, now even without her here I cant seem to get a rock hard erection (which i normally have), I am just worried basically is this all psychological? Or could something medical have came on this quick (it feels like theres not enough blood there, its like a weak erection but its still there and I can still cum). Any help/advice etc would be great, before I dig myself into a self-fulfilling prophecy of impotence at 18 lol. Id like to add, I smoke (for around 2 years now although since this has happened i havent had one, and smoke marijuana occasionally which i guess im gonna have to stop too untill this clears up) Im average if not slightly under average weight. Regards B.