HI,
I too have graves for over 25 yrs. Graves and low thyroid , like hashimotos thyroiditis, have totally opposite symptoms. Often when you are on meds for Graves , you actually may go low on thyroid .
High... fast pulse, high bp, loss of periods, thin depite ravenous appetite, thin hair, warm moist skin, tremor in hands, anxiety to name a few.
Low... slow pulse , low bp, heavy or more frequent periods, weight gain, graying of hair, tired, dry skin, slows your mental functions.
Sounds like it is time to do thyroid studies and a complete work up .
Thyroid disease is often discovered , or goes out of remission after pregnancy, upper respiratory infections and I imagine any stress.
I've been on the yo yo, so , you just have to be vigilant and follow up regularly.
My mom was diagnosed with graves disease about 13 years ago. For awhile she lived with it and then had to go through radiation for it. Well, after they had to finally do radiation on her thyroid and start her on medicine when her thyroid was basically gone, well, her menopause came back with really really bad symptoms that she thought she was having heart problems because of the sweats. She was about 60 years old, and had already gone through menopause around 45. It was silly that the specialists did all these tests, tested her blood and her heart and found her totally healthy and that it was just menopause come back. It's not supposed to come back 15 years later. Usually doesn't come back after 10 years. She puts up with the menopause symptoms because she'd rather be on higher levels of medicine than gain weight on lower levels. She swears it's from the thyroid medicine. It's not me, so I can't say for sure.
I would ask your doctor about it though. Periods every 13 days does not sound good. That means you are PMSingn every 2 weeks. Not to mention bleeding too often. I would not be happy if it were me and I would refuse to put up with it.