Yes indeed:) Ever since they put me on thyroid it has been better. Almost like obsolete. From 7 days down to 4 or 5. Now, on the other hand that pms stage is awful. I think you should get it checked. Good luck!
Yes it could well be your thyroid. For females the thyroid actually plays a very important role in regulating our menstrual cycles. Not always, as it can be different for eveyone, but generally, if you go too high, hyper, your periods lighten or stop. If hypo they can become heavier and more frequent.
You say you have been told your thyroid is either too high or too low at times. I wonder if you have had blood tests to show this. It could be Grave's disease you have and you may need medication. It could be Hashimoto's disease too, which has a similar effect of going up and down like a yo-yo over time.
Cheers!
I am not sure but wanted to stop by and say hi and welcome you to our community~!
C~