Lying about being a virgin

I live with my gma due to family issues. Me and my bf have been together for 2 years, (we started dating at 15) he is my first anything. After about 6 months I finally gave into sex and things. He was very patient with me through a whole hell of a lot. I didn't know how to kiss or be lovey, I wouldn't let him really do anything more than hold my hand for the first month or two (due to ptsd) He even called me babe once and I corrected him with my name. I mean come on who puts up with that? Anyway, my gma is very old school and doesn't think sex or BC is important in life period. I've asked to get BC since I was 16 (when me and my bf started "having fun") she told me no and told me this weird "horror" story. She keeps asking if I'm still a virgin and I keep lying because I don't want to disappoint her. I feel so bad lying to her because she always talks about how I'm so honest and that I never lie to her but I wanna tell her I just don't want her to treat me differently. Does anyone have any ideas on what to do or anyone else to tell who could help? (At least until I'm 18)