Hello Michelle.
If you're 21 and have not yet begun to get your periods, you should see a gynecologist for a thorough exam. At any rate, no one can tell you what this spotting means. There are many possibilities including stress, STD/STI, pregnancy, hormonal imbalance, etc. You need a thorough exam before diagnosis. See a gynecologist ASAP. Dr. J
If you had sex without birth control protection, it could also mean you are pregnant and this spotting is a sign of implantation. If you did not have unprotected sex, you are not pregnant and don't worry.
Its on its way....only cuz u stressed out it is delaying..