Severe nausea with start of period, no cramps. very heavey bleeding. been happening since baby, pp 5 months. what is the cause of this severe nausea.

Hard to know: if you are breast feeding your estrogen levels are very low and bleeding can be heavier than normal and could result in some nausea. Thyroid levels could be off and an early pregnancy could be responsible despite what appear to be regular cycles. It's hard to troubleshoot a situation like this in this type forum. You should consult your doctor if this continues to be a problem for you.

Hormonal changes: The changes in estrogen and progesterone levels that bring on the shedding of the uterine lining in menstruation have side effects, such as nausea, water retention and bloating, breast tenderness, headaches,, cramping, etc.