What Causes Periodic Pain In Left Breast?

I'm 24, and I'm pretty sure I'm healthy, well try to be, but yesterday and today ive noticed and ive been having a sharp periodic pain in my left breast, and not chest but my breast.and I just noticed a very visible vain from my pelvic area to my left breast, and also that the vains in my left breast are very brightly visible.more so thank normal
Should I bed worried?