Lump in breasts???

I have been taking OCP's for 4 months... But it's the first time my breast started hurting this much. I was trying to see if there's something wrong with it by examining if there's any lumps, I felt a small ball like thing but I'm not sure if its just a tissue bone or muscle that I can feel. What does a "lump" really feel like???? I just got examined 5 months ago. But when my OB did, it did not feel like she really took time to see if there's something there. I am not a skinny person, and I heard that lumps are harder to feel in bigger girls.. I need help. I don't wanna go to the doctor and have them say its only false alarm. HELP.