My periods just started becoming irregular but not sure what's going on.?

Recently my periods have been abnormal. I get 2 periods a month and sometimes skip a month. This is very unusual for me. My periods are usually on a regular schedule of 24 to 26 days and they last for 7 to 10 days. Ive always had bad periods. I am overweight and always have been so that shouldn't effect my periods now. I am 27 years old and I have 2 children. The change happened after my youngest was born. I've been to the doctor and she told me I needed bladder control therapy ( which makes no since to me). I experience cramping, break outs,mood swings, tender breast and nipples but I dont get period. I will end up getting two periods the next month. This is very unusual and I am concerned. I have had surgery on uterus because I was having so much pain. I also experience pain during sex and sometimes out of the blue. I get a pain in my lower abs that cripples me and I cant move for a couple of hours. I'm sure someone else has experienced this so I am looking for some advice.