Had my period two weeks ago and now i have it again. i don't understand why if i hadnt had intercourse in those two weeks. what could it possibly be?

Stress?: Lots of things can cause irregularities in your hormones, including stress, medications, travel, infections, and entering the peri-menopausal phase. If you are feeling well and do not have pain or discharge or fever, it is safe to wait and see if your cycles even out over the next 2 months. If not, see your OB/gyn or PCP.

Normal variation: How often you have your period is not at all related to how often you have intercourse. One doesn't affect the other. Your menstrual period is affected by many other things, however, including your body's hormones, stress, diet, sleep, etc. The normal interval between periods is 21-35 days; yours came sooner than that. You may observe; things will likely normalize next month. If not, see your doc