I've had this lump, size of a marble, with swelling/pain for going on 4 years now. It started in my right side, but is now also in my left. I've had over 30 tests to rule out certain things (such as lymphoma, mono, hormones, sti's, hiv, etc). Unfortunately, I still have not been given an answer as to WHY this is happening in my body. The lighter my menstrual flow, the smaller the lump and the less swelling. However, months where it's been heavier...my lump is big enough to see bulging out of my skin and the swelling is irritating and uncomfortable. Note: this does NOT just happen with my cycle, but also before and during my cycle. At different times each month.