So i'm a teen in high school, lots of friends, great girlfriend. She's interested in sex (oral, vaginal, etc.) and so am i. We've done stuff like she's manually stimulated me (idk if "j*rk me off" is allowed on the site) but no oral or actual sex yet.

So the problem is here. I'm a virgin (no thats not the problem). She wanted to give be oral in my car one time but I wasn't really feelin it cause my car is small and cramped. So I didn't get hard and we passed on it. Then another time we tried again in the car and I still couldn't get hard. I don't know if its nerves or jus being in the car. I have no problems masturbating, I mean I get a pretty good erection, nice and hard and i'm comfortable with my size, and in her bedroom she jerked me off no problem, but when she tried to give me oral in the car I couldnt get it up. Is it fear of not being able to get it up again, is it simply because doing it in the car turns me off, is it a combo of both, or something else? Any advice would be helpful.