What's wrong with my Breasts?!?!

A few days ago, my breast started getting really numb and sensitive, I didn't think much of it since my period was close. They continued to hurt for about 3 more days, then when I took a shower, I noticed that they got a little bigger and around the nipples it got softer and the circle around the nipples got bigger and a vain slowly started showing up around my left breast. The next day my period came so I'm pretty sure that I'm not pregnant, I'm only 16years old and not sure if this is normal and part of puberty or if its something else