My period comes on every 3 weeks for 3 days. i get severe cramps, headaches, and diarrhea.

Ob-Gyn can evaluate: Menstrual cycles are usually 28 days, but a few women have normal 21-day cycles. However, severe cramps are not normal, so an ob-gyn doctor can evaluate to see what the problem is, and to see why there is also diarrhea and headaches. Severe menstrual pain may be endometriosis, which causes some bleeding inside the abdomen during a woman's periods, and needs medical treatment.

Get GYN eval: Some options: Omega 3 fatty acid, magnesium, evening primrose oil, chasteberry. Magnesium, or black cohosh can help. Sipping chamomile can dissipate pain. Consider calcium, vit. B 6, or vit. E. Avoid excessive sugar & low-quality carbohydrate intake. Don’t add extra salt to your food & avoid processed foods. Reduce caffeine & alcohol use. Stay physically active.