When should I start wearing a bra?

I'm not like the others, wanting to wear a bra just because others wear one it's just in every book I read as SOON as they start developing they wear a bra. I have waited and I'm still small but they are starting to show through my shirt and they're big lumps (not boobs but ugly lumps) but what if my boobs stop developing or develop slower because I start wearing a bra. I know a girl who wore a bra as soon as she started developing (NOTE: I started developing around july or august 2010) and her boobs were all triangle-ish. Yuck! When I mean developing in july or august I mean they weren't any shape you could tell they were about to start (I'm not giving details.. most girls know because.. ʞʞɔnʎ ǝןdɹnd uɹnʇ sǝןddıu ǝɥʇ). Anyway I'm turning 12 in 12 days.. when should I start wearing a bra?! I hate bras btw