What size would I be in a sport bra?

That's a small, assuming you mean sports BRA.
I have no idea what a braW is..

Thank u

I'll just add, some sports bras are better than others. You often get what you pay for. When trying them on, you may want to do some jumping up and down to see just how supportive/restrictive it actually is. If you don't want to pay too much, you might find that doubling up on the bra works better than a single one on its own.

Yea a braw is a bra but that's just how I write it