too scared to have sex??

my bf and I have been together for a long time (3yrs) and we have had sex before. but his parents are super strict and will not let us be alone under any circumstances, and neither will mine. we want to be able to have sex again, and it looks like the only place we can do it is in his car. I’m just really scared of having car sex because I’m afraid of getting caught and becoming a sex offender or something, we are only 17. every time we’ve tried, I just get so scared that we can’t have sex, and it’s hurting both of us. what can I do?