According to the data you provided (erection when having foreplay, becoming flaccid afterwards, admitting that you are nervous), it is likely that you do not have problems with an erection. Men with erectile dysfunction usually can not have an erection at all if it is caused by a physical issue. These “problems” of yours are more common than you might have expected in younger males. Masturbation does not affect it either.


You are advised to learn relaxation techniques, which would help you reduce the stress. If you think that the stress is physical rather than mental (you try too hard), then why don’t you let the girl be the one that chooses the position, for example. If she is on top then you might keep your strength.


As for the fluid that comes out of the penis, you are likely noticing the pre-ejaculatory fluid. Pre-ejaculatory fluid is produced mostly by the bulbourethral glands and it prepares the vaginal environment for receiving the semen. If the person masturbated recently (few hours before the intercourse), then it might even contain small number of spermatozoids that are still viable for fertilizing.