I agree that you are overreacting. He probably called her shaker because thats what bellydancers do....I don't think it was in reference to the sex they had.
If you are going to ask questions about his exes/past, you gotta be mature enough to handle what he tells you. I'm not tryin to sound harsh, but this kind of thing can really turn a relationship sour.
For almost 2 years I brought up my boyfriends exes. Not even ex-girlfriends, they were all hoes he had sex with. We were 100% honest from the jump, I told him the number of people I slept with/oral/I told him everything. He told me everything. It made me mad: not at the time that he told me, but just randomly. I always felt insecure like, hmmm I wonder if she was prettier than me, or if she was better in bed?
Thinking about your boyfriend with other females is such a bad feeling....I just absolutely hated the thought. And me, being an immature person, decided to pick fights with him about it, and get mad and go on for days about it. Seriously, we had really really REALLY bad fights in our relationship. And why? Over some stupid girl that let him hit it while she was drunk? Well its none of my concern because we hadn't even met yet.
I'm just saying....its better to be mature and just let it go. Concentrate on having a healthy, fun, happy, positive, beautiful relationship with him. That girl isn't with him. Let her go bellydance her way to some other guy...because
he wants to be with
you. Don't pick fights with him...you will back him up against a wall, and confuse the hell out of him. I know it hurts, but theres nothing you can do about his past, and he can't change yours either.
...I wasted soooo much precious time of our lives and relationship, by arguing about silly nonsense like this. That time could've been spent..making love with him. Or kissing. Or talking, or laughing. But instead I chose to fight and scream and cry and hurt over females...who weren't worried about him.
You can't get time back, so spend it wisely.
Good luck!