No menstrual cycle for 3 years. first year pregnant, 2nd year breastfed, stopped nursing january 2021 still nothing. what could be causing this?

During pregnancy, a woman's hormones change drastically. It is possible that some kind of hormonal imbalance has developed that does not support the ovulation cycle. You will need a thorough exam by your primary care Dr or gynecologist along with labs to determine what is going on with your hormones. There are supportive therapies for hormone deficiencies.