Hematometra is an accumulation of blood in the uterus which would explain the endometrial thickening (I assume you mean "endometrial" versus "abdominal"). How thick is your lining? Hematometra is a risk of endometrial ablation and resulting pelvic pain.
If you aren't menopausal, the ovaries continue to produce reproductive levels of hormones which cause the uterine lining to build up. But since the ablation scarred the lining, the blood can get trapped behind the scarring. Another mechanism is that ablation can scar the cervix shut so that the blood cannot escape. I have read of some women having an in-office procedure done to stent the cervix and allow the blood to escape. Unfortunately, ablation is over-sold and many women are unaware of the long-term problems it can cause. A study published in 2008 showed that these problems can develop up to at least 8 years after the ablation and increase the risk for hysterectomy (to resolve the pelvic pain). I recall a woman saying that a gynecologist at a renowned east coast institution told her the procedure should not be done on women under age 50.
I hope you can get resolution without having to undergo hysterectomy which has its own set of short and long-term problems.