13 and I fit in a 30AA!? and no erect nipples!? HELP? ..?

Hi Im 13, Im really embarrased by my breast size! Im a 30AA ...my mam has quite small boobs and so does my nana. I dont really check their bra sizes because thats just vile. ;') anyway I noticed when I was swimming with my friends I felt really uncomfortable! I dont even have erect nipples they just pop out a little when Im cold or I rub against something...my nipple area is just all smooth! my friends fir into a 34B and 32B and stuff :( I feel upset coz I know ill get small boobs because my nana has them and my mam! I know we all grow at diffrent rates but I started my period and whatnot when I was 10! I dont wanna tell my mam! And I certainly dont wanna see a doctor!!! When we were swimming my costume pushed in my breasts so it looked like I was flat chested! Then my friend said to me..."dont you think it would be actually nice if you had something there? Does it affect you?" and I said yeah...HELP!?....