I'm a virgin, but i've missed a period.is this cause for concern after having amenhorrea for three years? or is it never okay to miss one?

Please clarify: Hi. After menarche, you went 3 years without periods, if I understand what you're saying. What, then periods resumed, and now you've missed one? Please tell us about why you were amenorrheic for 3 years (if known), what made periods resume (if known), and any other symptoms (male hair growth, breast milk production, headache, etc). It's OK to miss a period; you missed about 36 while amenorrheic!