What Are The Blood Filled Tiny Bumps On My Inner Thigh?

I just recently started noticing tiny bumps on my inner thighs and towards the inner butt region. They itch sometimes, and when I pop them, only blood comes out. I'm about to be 21, and I've never caught anything besides the occasional cold. I'm 5'4 and about 140. I'm just really beginning to get concerned because they are beginning to multiply and they seem to get bigger.