My menstruation is usually thick with large clots. this period, its suddenly watery with tiny clots. what could cause this? stress? nutritional?

Heavy periods: It sounds like your usual periods are worse than the one you are having now. There are multiple options for heavy periods. Hormonal treatments such as birth control pills, Progesterone treatments and the Mirena (levonorgestrel) iud are effective reversible treatments that will help many people. There is also a drug called Lysteda that contains no hormones which will help others.