Insecurity and jealousy

I have a problem more with myself than with my boyfriend. Here's the thing.

I am very self-conscious, generally I don't feel good with myself and my body and it doesn't matter how much I weight etc. because I've been feeling like this since I was a child. And you probably figured it out, I'm very jealous. My boyfriend is nice, he's good to me. But I can't stop thinking about the past incidents. When we started dating two years ago, when it started to be something more serious, I saw on instagram that my boyfriend follows a lot of accounts with almost naked girls. You know what I mean. I felt hurt, because I never was into looking at naked guys and it was hard to understand to me. But I talked to him, he said that they are some girls he followed long ago and stopped following them after our talk. I was like okay, like I didn't see he liked some of their pics a day ago, but OKAY, I didn't want to be exhausting and fight.

Last year we were at the lake with our friends. We were a bit drunk and were having a good time, until I saw that my boyfriend is looking at some girl. And it wasn't like he looked once or twice, but turned his head to her a few times. She was fit, tall, ver skinny, in a nice bikini. And well, I'm not fit, I'm a bit chubby. It made me feel sad, I know it's just looking, but situations like this make me crumble. He was drunk so when I asked him about it later he said he wasn't looking at any girl, but I'm not stupid and he was just lying. A few months ago I saw that he was searching some girls on instagram. Once again I tried to talk about it, but he said that his coworker took his phone and he was searching for those girls. Later there was the same situation and he said that it must have been by accident. To me that sounds like one of the most stupid lies ever said.

I would like to hear your opinion about this. Those are just some situations, it's not like he's ike this all the time. But it makes me more insecure, I don't feel good when we'r having sex because I have in mind that he likes prettier and skinnier girls. I can't forget about this and it's killing me. My insecurities are killing me and my relationship cause I can't get over it.

Am I crazy?