Fiancé and inappropriate jokes

So here's the thing. My fiancé, 34, and I, 32, have argued about inappropriate jokes before - jokes that are about me or even remotely about me. But here's a little background: I have bipolar disorder and borderline personality disorder, both of which can make me ultra sensitive and emotional, and even feel personally attacked (I've been on meds, in hospitals, in therapy). It's just how my brain functions. After three years of being together, I'd expect him to know what can potentially trigger me, but I guess that's not the case. When we first started dating, he and his younger brother would act so immature, and my fiance would even make gestures about me giving him a blow job as a joke. At first he'd get defensive and say I was being sensitive but eventually he got the point and stopped. But today I was telling his brother how the two female physicians at my doctor's office are attractive but older ladies. I said "right? They kinda are." And he replied like a robot "I wouldn't know, you're the only beautiful woman to me." His mother burst out laughing, I guess because of my facial expression as he was talking. To extend the laughter, then he started telling his brother, his mom and myself about how a few months ago he was draining tuna in the sink and said "Great, now my hands are going to smell like tuna for a week." Apparently his mom started laughing hysterically (with her mind in the gutter) as he asked her to tell him what she was laughing about (and she never did, bit he knew what she was thinking). I'm sure I'd never heard of that joke because he knew it would bother me, but what upset me was that the first time I heard about that we in front of her and his brother. They have that kind of relationship, I guess, where even gross or inappropriate things are funny, that's just not the way I was brought up. I have a sense of humor, but with certain things I just think it's about respect. He claims that I just want to be mad at him for something, that his family is good to me (and they are) and that I'm just making it out to be worse than it is. My argument to him is that just because him and his family are good to me doesn't mean my feelings aren't valid. Am I overreacting or being ultra sensitive? Should he be more respectful?