Hi. I agree with the others. It is not too early for a mammogram. I, too, had lumpy, bumpy, painful breasts from my early teens on. I did regular breast exams, so I knew what my "normal" lumps and bumps felt like, which ones came and went...but then I found a tiny lump that felt different to me. It wasn't painful. It just wasn't like the others. So I watched it a couple of months to see if it changed or went away, and it didn't. I called my doctor, and he did a breast exam. He found a second tiny lump, much like the one I had found. I had a mammogram, which was "normal." And he insisted I see a surgeon and have the lumps biopsied. Everyone assured me that "it was probably nothing, but just to be sure..." The lumps were both invasive breast cancers, and of different types. I was 36 at the time.
Had I gone to a doctor who based his decision on a mammogram, I would not be here 12 years later to tell you to insist on not only a mammogram (which misses something like 30% of all breast cancers, especially in young women), but to see a surgeon and have a biopsy if you are not comfortable with the answers you get. I don't know if you have a center that specializes in breasts, but most larger cities have them, and I would ask for a referral to one, if possible.
Pain is not generally associated with breast cancers, it is more typically associated with cysts or "fibrocystic breast disease," which is basically lumpy, bumpy breasts. However, pain does not rule out breast cancer, either. Some women report their breast cancers as painful. You need a definitive answer that you are comfortable with. Don't settle for a doctor who leaves you worrying.