Hi Veena. There is tendency of the menstrual cycles to vary one if your thyroid functions are not in normal range and two if you are a perimenopausal woman. You mentioned that your thyroid was checked two months ago and that time TSH
was 5.95 which has fallen into normal range after taking the 12.5 micrograms of levo-thyroxine
. But I would suggest to check the TSH after 6 more weeks from the last check up and also check for 'Anti-TPO'. These are the antibodies
which are common reason for people to have autoimmune hypothyroidism
. And if you are positive for the antibodies then it's likely that your dose of levo thyroxine goes higher. Other thing, if you have a family tendency (like sisters and mother) of menopause
by around 41 years, then may be you are also perimenopausal and this is leading to the erratic cycles. Take care.