Hello doctor, I am 20 year old girl. Actually I am having left breast pain. I don't know what is it. I also have pain in my arm but there is no lump. When I wear tight clothes it hurts a lot and when I don't where undergarment then I feel pain but when I wear bra then it feels good. There is no nipple discharge. But I am very scared that what it is. Usually pain starts when I don't wear undergarments. I have pain in my breast and near the breast area as well. (like below the breast and upward). Please help me out in this regard.