21 yr old female, 22 monday. I'm freaking out because one of my breast is swollen, lumpy, & sore along with back pain on that same side.?

Possibly serious. You need to see your doctor immediately. Sometimes this could be a bad infection but also a much more seious issue which you will need treatment for without delay. I cannot say this too strongly.
Cysts? Are you close to your period? It would be unusual, but multiple cysts could make one breast sore, and swollen. I am not sure how it would make your back sore. Please see a doctor quickly, to have an exam and maybe an ultrasound of your breasts to figure out what is the problem. Let me know.