I think it is time to check your thyroid. Sometimes as you age you will need thyroid medication for replacement after Graves' disease treatment.
One of the most common cause of prolonged irregular bleeding and someone who formerly was regular is the onset of hypothyroidism
or under functioning thyroid.
You're young for the onset of menopausal symptoms which also is associated with irregular cycles unless your entire family goes through menopause
I hope you feel better soon. I'm sure between the endocrinologist
and the gynecologist they will figure out what is going on and correct it.