Your body could be producing elevated amounts of progesterone and estrogen. Speak to your doctor further because sometimes it is a sign of uterine cancer.
Endometrial lining thickens when you have your periods and ovulate. It thickens more when you are pregnant. So either you are having your periods or are pregnant.
It is very common for a females endometrial lining to thicken at the beginning of every menstrual cycle. This is the normal process of preparing your body for a pregnancy.
