That fact that your boyfriend's best friend keeps cracking these jokes signifies to me that your boyfriend has some boundary issues he needs to work on. The friend is clearly being obnoxious (and given that I don't know why or how the jokes got started in the first place) and is just running with his jokes because the boyfriend doesn't say anything.
Which, to be clear, is pretty disrespectful. Unless you all were best friends first and that was par the course for the relationship, it's not okay. And even then, it should be tempered.
I think you need to talk to your boyfriend since its his best friend. He needs to know that you don't like the jokes and they make you uncomfortable. You should also let him know that you feel uncomfortable with his willingness to allow his boy to talk about you in such a fashion. That makes both of you all look bad. If the boyfriend doesn't step up to the plate well then you go straight to the best friend and tell him that he's a disrespectful d-bag and he needs to fall back from talking greasy to you.
The problem here is that he'll look to your boyfriend who probably won't say anything and then he'll go harder.
So basically, you'll end up breaking up with your boyfriend if he doesn't handle it. So let's hope he does.
Cheers.
Did l do the right thing? When a guy l have had sex with I find out that he was having sex with someone I knew that work. She knew about me and said nothing to me. I broke. I broke. It off with him seven. Months. Later he gives. Me a disgusting look walkby and act like it didn't. happened