What Causes Severe Cramps During Ovulation And Menstruation?

i had a uterine ablation in 2008 and had no bleeding or cramping afterwards up until 8 months ago. Even before the ablation I had what looks like tissue sloughing off when i urinate. It occurs around my period and when I am ovulating. Also I have been getting severe cramps during ovulation and during my menstration. I can't go on any type of hormore treatments due to a DVT and I because I was recently hospitalized for a pulmonary embolism. What can it be? My gynecologist has no definite answer for me. Do you have any idea what is happening? Is it hormonal..., can the tissue grow back after a uterine ablation? Your help is greatly appreciated. Sincerely TJ