I had sex Feb. 15, I got my period March 6th, it was normal, nothing different about it. I havent gotten mine in April. My calendar app's tell me i am 18 days late. I am usually later than the calender, but not this bad. I have been walking alot more, to try to lose weight, and stressed with finals coming, could this be the reason I am late? I feel as if my period is coming, but every time i check, its not there. Please Help!