Menstrual irregularities are common in women above 35 years. As the age increases the levels of Estrogen and progesterone
vary in the body. Due to variation in these hormone levels the duration of cycle changes. There are other factors which can affect the menstruation
like stress, body weight, low hemoglobin
levels and medicines if any. There is nothing wrong with you. As i mentioned earlier it is quite common at your age. I would recommend you to please get your Serum Estradiol
, progesterone and prolactin
and Thyroid hormone levels checked. Based on the results you can take appropriate medicine after consulting a gynaecilogist.
Wish you good health
Take care and Bye