What happens it the uteras walls are to thick?

Wall or lining?: Is the lining of the uterus thickened or the wall? Unusual thickening of the lining of the uterus (endometrium) can be a sign of hyperplasia, polyp, or neoplasm. Thickening of the uterine wall itself probably indicates fibroids (benign tumors of the uterine muscle).

Do you mean lining?: You probably mean the lining of the uterus, not the wall. If the lining of the uterus is too thick then the chance of abnormal or pre-cancerous or even cancerous cells increases. This is something that should be evaluated by your obgyn.