Parents & Sex

I'm 17, almost 18 and I've been having sex since I was 16. I've just had sex with one person and it's been with my current boyfriend whom I love and trust with all my heart. Unfortunately my parents are very overprotective of me and I don't feel comfortable telling them that I've been sexually active. They are very open with me (specially my dad) but he's always talked about sex like if I was stupid enough to get myself pregnant or get an STI. I am smart and so is my boyfriend and we've always used protection and made the correct choices. My boyfriend is very respectful and he takes very good care of me. He would never hurt me or disrespect me. He's 28 and I'm 17 but my parents and his have been very understanding about our relationship and they've let us be together and whatnot but they've always freaked out about the sex topic. I mean we know how to take our precautions and be careful but somehow I still don't feel confortable to openly talk about my sex life with my parents. I feel as if they'll insult me or call me words and stuff :( I really want to be open with them but I don't feel comfortable about it. What can I do? :(