Welcome to HCM
We understand your concerns
Your problems seems to be purely psychological. The heating of body during sexual pre play is very much normal and mild sweating is also normal. But you are apprehensive of these things. You are anxious about your performance and therefore your erection is not normal.
Leave the anxiety
away. Sex is not everything in life. Give sex little weightage and you will perform better. And for a start, do not masturbate for atleast a week and then approach a girl with confidence.
Wish you speedy recovery.