Worried but not Diagnosed

Hi everyone. So a little bit of info. I'm only 21 years old but am having issues with my right breast. About 5 months ago I noticed a movable lump in my right breast near my armpit/side. A week after I noticed it, it had doubled in size. It was tender and causing shooting pains running from that spot to my nipple. In that time my breast also doubled in size, while my left stayed fairly the same. I went to a breast cancer center for a mamo and ultrasound. The doctor felt the lump and said that it seemed fine since it was movable. The ultrasound found nothing but "normal breast tissue that was thickened". This was three months ago. Since I have had tenderness and the 'lump' has now spread in a crescent shape around the top of my breast. It's about five to six inches long, and my breast has swollen even more, to a little over double the size of my left. My right nipple now points downward whereas my left does not. And my right nipple has become huge.. I am very concerned but cannot go back to the doctor for financial reasons... I have pictures but am aware that we cannot post them here. I have had no rashes.. no change in nipple protrusion, only nipple size. There is warmth to the touch, and the veins in my breast are enlarged in comparison to the left one. (Though I'm aware this is probably due to swelling.) I do have a family history of Breast Cancer.

Has anyone else's BC presented this way? I realize that I am very young to be worried about breast cancer.. but in my heart I know that something is wrong, whether it be BC or an infection of some sort. Any answers would be wonderful.