Boyfriends mom

Okay so me and my boyfriend have been dating for 2 years he's 18 and I'm 15 (we have had sex a few times) but anyway his mom seems to think that's all we do and she won't believe when we say that's not it and she hates the fact I'm 15 yet her and her husband are exactly 3 years apart like me and my boyfriend and she had sex at my age as well I just don't understand and I don't know how to get her to stop hating me I haven't done anything and like when we had sex she told her son it was his fault that I had no idea what I was doing I'm only doing it to please him like wtf??