lacking confidence/low self esteem

I'm lacking in confidence. Especially around my boyfriend. I've always had low self esteem but lately it feels worse. He finds other women who are completely different to me attractive. We were out with friends once and he made a comment about a girl who walked passed and it really upset me. I didn't say anything at the time and discussed it a week or so later with him, he said that it was nothing. I have quite small breasts and when we have sex he asks me to push them together. I'm usually fine with this but the last time he said it I just started to cry and got really upset. He looks at girls  nudes online who have had implants and I just don't feel all that attractive to him, I feel really uncomfortable being naked around him. Any other girls feel or felt this way?? I feel like it isn't his fault but mine because I really lack in confidence.