Thanks for the query.
According to your description the possibilities are:
-menorrhagea and inter-menstrual spotting due to fibroid
So you consult gynecologist once and go for physical examination and ultrasound
to find out the possible cause and take treatment accordingly.
If your doctor suggests go for thyroid
For more details you can ask me through: http://www.healthcaremagic.com/doctors/dr-sree-gouri-sr/63429