I believe you posted this on the wrong forum. However, I will try to answer your query.
Are your periods regular? The fact that you had your period indicates that you are not pregnant. To be sure, you can take a pregnancy test. There are numerous factors which could cause a disruption in a regular menstrual cycle, including uterine conditions, endocrine disorders or imbalances, and stress. It would be advisable to monitor your cycle for the meantime and if in the next few months your cycle is still not regular, you could consult an ob-gyn doctor. If you are very concerned about your condition, you could consult one as soon as possible.
Hope this helps.