Self conscious and I can’t seem to get over it

Hello! So I’ve always been naturally thin, but I have a bit of a booty😁 I wouldn’t say I’m unhealthy I’m just skinny. I never used to wear shorts because I hated my legs but started wearing shorts and skirts and now it’s like a normal thing to me. I’m going g to start working out to gain muscle (I’ve gained about 15 lbs but don’t really notice it)... I’ve made a lot of progress in feeling confident in myself which I’m proud of. The only thing I can’t seem to feel confident is my boobs. I have a basically flat chest and I absolutely hate it. My boyfriend loves me the way I am and always lets me know that. But I can’t seem to get over how embarrassed and self conscious I am about my flat chest. It doesn’t help that I don’t want to get fully naked in front of him and when I do I cover myself with my arms or blanket. (I know he gets a tiny bit frustrated because he just wants me to be comfortable in front of him)..... When I lay down my chest is completely flat I’m going to be 24 soon and I just feel less feminine because of how small I am up there.... I don’t want to have surgery as I’ve heard that you could get Brest implant illness and I don’t want to risk it... any tips to help me? I really want to not care so much about it but I struggle so so much...

-L