la petite moi

I am 18 as of 22 April. Alright, so a few months ago, I finally told my mother that my boyfriend and I have been having sex. At the time, we had probably been going out for nine months. We use condoms occasionally, and we have to drive at least 15 minutes to get my birth control shots every three months (which hurts like crazy for me). My mother knows I'm safe.

However, now it's getting out of hand since she knows. She doesn't CARE necessarily, but she uses it to 'tease' me, of sorts. If I wanna go camping with him, it's so that we can get in a tent and fuck the whole time. If I go somewhere carrying a blanket when my boyfriend's around (I get cold very easily), she thinks I'm using it to cover up sex. If we go for a walk at night, she thinks we're going somewhere to fuck.

Tonight this is how the conversation goes:
Me: Mum, do you know any good places Nwlinkvxd and I can go camping?
Mum: No not really. (And actually, my mother goes camping and hiking every other week.)
Me: Sure you do.
Mum: Yeah, but if I tell you, you'll just try to avoid them since I like them...:snort:
Me: No, I won't.
My sister: Jeez, that's dumb Mum. The places you've been are beautiful.
Mum: So...you two are using a tent together eh??? :snort:
My sister: WHAT?!!! What's your problem???
Me: Nothing, (sister's name). She just thinks I'm having promiscuous sex.
Mum: No I'm not. You're just fucking your boyfriend...

My sister got SO pissed and shoved her out the door to our room. It's unfair that I try to be very safe and responsible with sex, and she just makes jokes about it.

Is there ANYTHING I can say or do to make her stop???