If it makes you feel any better, I scored the same (was probably like 'B' pre-HRT just from being overweight) and I decided to try wearing tanks with built-in support for undershirts because one of my shirts seems to sometimes get pokies with just a normal loose T-shirt under it. Because its a white tank, you can kinda tell it has an extra layer around the chest if you look closely and its a snug fit. I asked my brother and my cousin yesterday if they thought my parents would ask questions if I just wore that. And my cousin was like "questions about what?" and my brother seemed to think I was just asking it being a tank-style shirt instead of a normal t-shirt? And they both know I'm on HRT. Neither seemed to notice the more boob-like shape or the bra.

I'm still a smaller cup size than my cismale no-HRT super-obese cousin (granted, the shape is much less boob-like).

So... I wouldn't worry too much about cismales noticing unless like you are showing off cleavage or you get a fair bit bigger. Also, so many people simply don't know what HRT does, so they'll probably just assume you put on weight. The main groups that would notice are probably trans people and female trans-allies.

i've found that i've had to downsize a bit, yeah. a lot of us have shallow breasts and i think the site isn't that good at finding a bra size for that breast type

Boobs too big 😔✊️

Use a calculator! You need a tape measurer too, like a proper floppy one you can wrap around your rib cage and boobs. Don't be disheartened if it's smaller than B. Then again, you are pretty small you actually might be.