Uterin Cysts

Hi, I recently visited an urgent care center because two weeks after my normal menstral cycle I started spotting old blood (brown in color) for about three days. It was associated with lower abdominal pain (almost like a contraction just before giving birth) and pain in my back around my kidney area. They ran an MRI or CAT Scan (drank a liquid and induced dye), but no other tests, and they found cysts in my uterus. They were originally looking for kidney stones (none found) but they discovered cysts in my uterus. They did not tell me to what extent or how large....or really anything at all, except they recommended I see an OBGYN. This was back around in the first week of July. Well here it is Aug and I have again spotted the "old" blood for a couple days and nothing else. I have not had a normal cycle since mid June. Is this something I should be alarmed about? I am 36 and thinking maybe it's all just part of lifes cycles. I am not pregnant because my tubes were cut out 13 years ago after a difficult pregnancy and labor. What could be causing the abnomalities after a lifetime of normal cycles? And what might be causing cysts in my uterus? I'd really appreciate any information you can give.

Thanks,

Kimberly