If you are taking estrogen, even in very doses, you will likely, in time, develop breasts. It's what estrogen does.
With that said, I have had A to B cups moobs for over 40 years, and it has never stopped me from presenting male.
Now, what did MtF trannsexuals do before the 1930s and the advent of hormones? They coped the best way they could. Sometime dressing. Sometimes living "stealth."