Hello, thanks for the query.
You have two separate problems.
1. Excessive menstrual blood loss is called menorrhagia
. Most common cause in your age group is fibroid uterus. Get an USG done for diagnosis and get treated accordingly.
2. Passing scanty urine on increased abdominal pressure indicated stress incontinence
. This is due to atonis pelvic floor
muscles. Treatment is to increase your pelvic muscle tone
by doing kegels exercise.
hope this helps.