I'm sure this will be deemed nonsupportive, but your insecurities and low self esteem are not your boyfriend's responsibility to try and fix. Only you can fix your self esteem. Dumping the guy isn't the answer. If we dumped every guy who fantasized about some unobtainable breasts, we'd be a lonely lot of people.

You could stop if you wanted to, but you must be getting some reward out of continuing to beat yourself up emotionally.

Just my take.