Hi.
Thanks for your query and an elucidate history.
To consider your history one by one:
The cause of the lower abdominal pain can be many.this can be due to PID, due to the mass in the uterus as per your ultrasonography.
It is possible that there is a prolapse of the uterus giving you typical pains of the type of
menstrual cramps.
In addition taking the biest and progesterone as a
hormone replacement therapy can have its own effect on not only the uterus but also on the body and can give wright gain and all associated symptoms.
Frequent urination can be due to
urinary tract infection or prolapse of the uterus as has been mentioned above.
I would advise you the following::
Blood tests , particularly of the hormonal status including the
Thyroid function tests.
Urine routine , microscopy, culture ans sensitivity.
Ultrasonography of abdomen.
Physical examination by a Gynecologist to rule out any prolapse and so.
Currating and biopsy of the endometrium to rule of the cancer.
All these tests will lead to a proper diagnosis and plan for a proper treaetment