I've never given blood because I don't weigh enough for my height.

I don't believe any of the myths. Blood type is labeled because of the antigens (did I spell that right? XD) on your blood cells. They're like ID tags just like RH. I've actually been studying blood types along with genetic disorders for a while these past few months.

My technical blood genotype is Bi RH+ which of course can be abbreviated to B+
I got the 'B' from my dad and the 'i' from my mom, because she's O+.