If you've had a recent blood test for your thyroid gland can you get a print-out from the surgery, with the ranges so that members can comment upon them. Always get a copy of your blood tests for your own records and so that you can post if you have a query. If you haven't had Vitamin B12, Vitamin D, iron, ferritin and folate checked ask for these to be done as we are usually deficient. You don't take medication before your blood test, take it afterwards and have it as early as possible.
As you are still feeling unwell on 175mcg levo although your GP will think your results are 'good' as they are in range, some of us need a very low TSH or even suppressed to feel good. Most of us feel better with the addition of some T3 (liothyronine) added to the T4 (levothyroxine) and sometimes a reduction is made to the T4.
If you email firstname.lastname@example.org and ask for a copy of the Pulse Online article by Dr Toft and question 6 should be referred to. Ignore is last para which is typical I think of many in Endocrinology. There is also a suggestion of the addition of some T3. Dr Toft was President of the British Thyroid Association.
Maybe you've been undermedicated for a long time which has maybe aggravated your periods problem.
This is another link to an archived website but has good info and other topics are at the top of the page. Some links within may not work.