21. rarely regular periods, sometimes severe cramping and vomiting, last one 4 months ago, the period before that was five months late. gyn ok. y late?

Hormonal: Your hormonal cycling is not normal. You may not be ovulating regularly. You should see your primary care provider and get this checked out.

Not okay: Sometimes delayed periods can be due to hormonal imbalances, often they are due in many americans to being overweight. Sometimes being underweight can cause as well. Bottom line, absence of menstrual cycle needs to be evaluated by a gynecologist to make sure you aren't possibly placing yourself in harms way. Definitely make an appointment to be evalauted, good luck!