Cramps/pain

Hi all, I'm not sure if anyone has experienced this before or not but ...
I've recently gone off my birth control (depo- been on for 2.5 years) in hopes that we can have another baby sometime soon. I have been off for 2 months now and I'm starting to have really uncomfortable cramps in my lower abdomen. I'm seeing my dr but we don't know what it is. I have an ultrasound tomorrow. I'm not pregnant, we took a pregnancy test, I don't have a period (could it be period pains even though I don't get one?) and I'm not ovulating (I took an ovulation test) my pains are constant. I was thinking maybe a cyst ruptured? My doctor says it could take up to 2 weeks for the pain to go away. It's been about a week now. Thoughts? What else could this be? Has anyone ever experienced this coming off the depo? Does anyone have any idea what might be going on with my body?