I bought a tape measure so I could try and track growth progress, and I figured I would try to get my bra size. Long story short, I took some measurements while wearing a non padded sports bra (trying to get some consistent numbers,) and after plugging said numbers into a calculator, I think I am a 42A. Not 100% sure as I guess I have always seen myself as having "pecks" and not boobs, but maybe it's right.

Guess I would like to grow some breasts that I know are actual breasts, and aren't just muscle.

Trust me, get fitted professionally. It won't cost extra.

Once I get some noticeable growth I think I will.

Well, the alternative to a pro fitting is trial and error. When I first started buying bras online I tried using the store measurement guides and was completely wrong. The guides vary from one store to another and the actual sizes vary from one manufacturer to another. This it true of all women's clothing, in fact. I had to buy a couple of bras to figure out my actual size. If you have to buy your first bras online, be sure to make the cheapies because they may not fit. Even after you think you know your size you can still score a non-fitter now and then.