you could have a cyst on your ovaries..your body may be confused by not having a period and a blood clot could be stopping you up due to the cyst I know from personal experience..whatever the case may be i would go to the doctor or the emergency room ASAP
If you are sexually active, i would buy a pregnancy test & for the best results take the test in the morning "Ur 1st Morning pee" because that's what has all your hormones in it!! Also if you are on any type of birth control it can do this. If you were spotting in between your periods its because of Ur hormones changing. Good luck.
If you are sexually active and you didn't use any kind of protection then you are probably pregnant. You need to go to a doctor. And for your own safety you shouldn't post personal info like this on a website.