How much should I worry about amenorrhea?

Get evaluated. Amenorrhea is not normal, can cause osteoporosis and affect your well being, besides afecting fertility. First, a pregnancy test should be done and then other tests to find out the cause.
Can affect fertility. If your brain isn't signalling for an egg release from your ovary, you won't have a signal for your periods either; that's usually the cause of amenorrhea. Often it's a hormonal imbalance--Thyroid, Prolactin, LH, FSH, Hcg should be checked. Your doctor can also induce a period as well w/ OCPs. If you've NEVER had a period, you should get an US to make sure you have normal uterus/vagina/ovaries.