BRAAA SIZE HELP!

I used to wear sports bras then started wearing wire bras last Oct(?). I've been only wearing 38 B and just recently I asked my mom and she said it's too big. I thought it might be too big but also too small. The reason for it too big is the cup has space between my boob and the bra. I did measure my self and it came out 38 aa and I've been researching and I'm not sure if that's a conversion size for 38 B or if it's something else. I just need help figuring out what size I need and it's just all so confusing.