Seconding Amanda's advice about getting to a doctor. I don't know too much about the American health system other than it's completely different from ours - are there any free or low cost clinics that you can get to?
Wee bit of personal TMI here. I found a lump in my breast in January of last year. We do have a history of breast cancer in my family - a cousin died at 38 as a result of secondary cancer, so you can imagine how I felt. I went to my GP who told me that something like 90% of all lumps are not cancerous, but tend to be cysts or similar - mine thankfully was a cyst.
Do you have a family history of breast cancer? It can be genetic, but not always. You're also quite young to be diagnosed with breast cancer - it's quite rare for a woman of your age to develop breast cancer. In saying that, it's not unheard of, so please do get yourself to a doctor.
Take care