Would you be with someone you were too insecure with?

I been with my bf for over a year and never can get fully naked. I’m thin and about 130 pounds 5’6/5’7. I never take my shirt off during sex because I hate my boobs since I was small. I feel like they never ever grew. My 13 year old cousin has a bigger chest than me. I wear push up bras and even then it looks like nothing. I took pills, lotions, everything! Nothing worked. My mom said hers didn’t grow till after she had kids. However, I’m only 20. my sister didn’t have kids and she’s a almost a C if not a C already. And she’s 30. He always gets on me about it and makes me even more insecure. He’ll tell me my boobs are big and all and I know hes lying which makes it so much worse! Advice please? I’ve been fighting this battle for years.