right breast pain and swelling bad ??

i’ve been having a sore tender pain in my right breast for a couple months now that’s just getting worse . my right breast is swollen a half cup size bigger . it’s also leaking thick yellow fluid from my nipple . i did breastfeed almost 2 years ago , so i’m not sure if that’s contributing to the discharge . the pain goes from under my armpit all down the outside half of my boob . i went to convenient care and they scheduled me a mammogram i was supposed to have this friday , but they called me and told me i have to have an ultrasound instead since i’m under 30 (i’m 20) . it’s scheduled in 8 days . at the convenient care they did a breast exam and she told me she can indeed feel something inside , and it definitely is swollen . i am so terrified . cancer runs on my dads side of the family bad . i’m hoping to god it’s a cyst or something . i’m hoping to hear if anyone had the same symptoms as me and it turned out to be nothing serious ?