Lack of trust gone too far

I've been with my boyfriend for 2 years and have been battling his lack of trust for just as long. I keep hoping that he will realize that he has nothing to worry about with me. He doubts me so much and I feel like I have proven myself over and over again. It makes me feel so low every time he questions and doubts me. His doubts start if I miss his call or take too long to answer. He'll assume I was on the phone when I was not. If my schedule changes at work he thinks I'm lying. I just have to do way too much explaining and it's tiring. But I still have hope and want it to work with us .

This last time was too much for me. I told my bf I felt a yeast infection coming on. He told me he thought I was lying because I didn't say anything all weekend or earlier that day. I told him I can only say something when I start experiencing the symptoms not before (he's accused me about lying about a yeast infection before because I didn't tell him until after I got the medicine). I don't understand what he thinks I would gain from lying about a yeast infection. I don't even like talking about it. Things got kind of ugly and he told me he wanted his key back. I said ok.

I got to his place and we talked /argued. When I got really upset and said I was done he wouldn't let me leave. He was blocking the door and making me go to the back of the apartment. I got loud. He got loud. After things calmed down some he said he wanted to see my vagina/yeast infection. I didn't understand what he meant and thought he would see but he was insistent. I have such a strong urge for him to understand me. I gave in because I didn't want him to take my refusal as if I was hiding something. It was a mistake. We go to his room. He takes my pants off and starts inspecting my vagina in a technical and cold manner. I told him I didn't like it and I was uncomfortable but he said I shouldn't be because he's seen it all before. He's touching me and moving his fingers around to see how I was. He smells me then licks me I guess to see if it tasted different. I wanted to cry but I didn't. Somehow in all of this we were turned on and had sex. As soon as we finished he started talking about how he didn't believe me again. I was so upset and hurt. Why did I let it go that far? I felt humiliated and violated. It sounds crazy to me that he thought inspecting me like that is ok. Even crazier that I let it happen and didn't stand up for myself. I still want us to get better but I don't think it's anything else I can do to get him to see that in serious about us and faithful.