My left breast has gotten bigger and there is a lump on my areola with a bright red vein looking mark going across part of my chest and it is tender?

Mastitis.: The breast is basically a glandular structure and can get an infection much like a pimple. Unfortunately breast infection gets a whole lot worse and hurts a whole lot worse. Go see your doctor as soon as possible

Mastitis vs tumor: Your complaints are worrisome and firstly you have to see your fd/gyn asap to rule out infection and treat with antibiotics if not better or resolved within one or two wks then you need biopsy to rule our inflammatory breat tumor although it is rare but do happen in your age group. Good luck and act soono

Do not wait: See a general surgeon first, especially one with an interest in breast diseases