Since you have mentioned
thyroid and PCOD problems and yes you are correct that can be one of the reasons but it's more likely if you are gaining weight as well. So my suggestions would be get and ultrasound abdomen done along with a blood test for thyroid levels. For now if bleeding still continues you can take the following medicines. 1. Tab. Meftal spas 1 tab 2 times a day, 2. Tab. Stiplon (Himalaya) 1 tab 2 times a day to reduce bleeding.
Next Steps
if bleeding purchased beyond 10 days consult an ecologist and get an ultrasound abdomen done.