My cervix is high and hard. my period was due 3 weeks ago. negative pregnancy test. what does this mean?

Late for period: I'm not sure what the reference to your cervix implies, as checking one's cervix isn't typically a sign of anything. It does however sound like you are having irregular period, given that you are 3 weeks late. Irregular periods can be due to hormones, thyroid, weight issues (thin/heavy). If continues, consider seeing a gynecologist. Best luck.

Not likely pregnant: A cervix that is high and hard is normal. A negative pregnancy test, when three weeks late, should be reliable. This is likely just an aberrant cycle. At any rate, consider an evaluation by a gynecologist, especially if neg pregnancy test and no period in the next 9 weeks.