Am I a good size?

I'm a size 8 in clothing and a 34 B cup size...I've had my friends tell me how much they want my body but I don't see it. I'm self conscious about everything. Even during sex I leave my top on and bra, I don't know what it is. I just really don't like my upper part of my body :(

What should I do to get the confidence I need? I do go to the gym and do sit ups and everything but it doesn't seem to be working...is there any other workouts that I could try?
Am I a good size?
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