I had a semi-painful mass too, which I had removed and biopsied. It turned out to be a fibroadenoma. Since you are very young, and since you have not mentioned any members of your family that have had breast cancer (especially mothers, aunts or sisters), I would say your risk of cancer is low to quite low.
A palpable mass just means they can feel the mass by palpating it, or mashing on it...it's not a particular kind of mass....since they can feel it, they just want to check it out. I agree with Jayay. They just want to follow it along. As long as they keep monitoring you, you are in good hands (no pun intended there)
As a general rule, if a breast lump hurts, you're looking at a benign cyst. Caffeine is a big-time culprit in breast formation. It's likely you have no trouble as far as cancer is concerned, but your docs want to keep an eye on things - which is a good idea. It sounds like you're getting good advice and care from your doctors, so keep doing what they ask you to do.