Out of control jealously!

Ok so the other week me and my boyfriend went away on holiday and I heard he was basically the village slut there from when he lived there. I was really on edge when someone pointed out one of his weekend flings from years ago. I asked him about her to see if it was true or just people trying to wind me up and he agreed and said he had slept with her multiple times. I got so upset I walked out and back to our hotel where I burst into tears. He followed after me and asked what was wrong so I explained to him I felt really crap cause she was the complete opposite of me.
​She was thin, blonde, short and dead gorgous. 
​Lately we have had loads of distance cause he has a new job miles away from me so it's hard to see eachother unless he gets weekends off. So obviously my paranoia and jealousy has gone mad! 
​Anyway. After a month of not seeing eachother he didn't want to have sex. (Tmi I know but it needs to be put out there.) and that really upset me. So to see his ex fling in the pub and see how different we are was a confidence crusher. (Killed my confidence further finding out she's actually a model) after seeing her and getting over the upset he told me about all his ex's then told me I looked like one. After seeing her (I really looked nothing like her beside the fact we are both about a size 16-18) her face was horrifying! Honestly I don't mean to sound bitchy but she looked like a run down giraffe on crack. Now I feel shit and I just need someway to get it out my head. I've tried the whole "he's mine now so I won" but it just doesn't work. I just need some help. Am I just going crazy? Help? :/