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Your symptoms suggest that you have a condition known as endometriosis.
This is a condition in which cells from inside the uterus forms in other sites like the ovaries, cervix etc. They need to be cauterized off.
But there is always the risk of recurrence and , in your case, is is very likely that you have had a recurrence of the condition.
Endometriosis can cause very severe pain during the periods.
Endometriosis can also cause stenosis of the cervix. And if the doctor was unable to dilate the cervix to insert the IUD, then it is likely that you do have stenosis. Stenosis will cause pain too.
You will need a procedure called Hysteroscopy in which a camera will be inserted into the cervix and uterus and any stenosis can be opened up and an IUD inserted. Endometriotic cells can also be cauterized at the same time.
You can also have a laparoscopy at the same time to remove any endometriosis inside the abdomen.
Please consult your Obgyn.