I'm twenty years old and not on birth control, I became sexually active about four months ago. My partner always "with drawed" before he came. My period has always came during the month and I never kept track. Silly of me not to once I became sexually active...I must admit. However this month I experienced hot flashes and some of the familiar symptoms of my period. Breast tenderness did not accompany the cramp like pains. For a short period about a week ago my nipples were sensitve and well, aren't anymore. Anyway the period never came. I'm not 100% positive when my last period started making things increasingly difficult to figure out. For the last few months I've noticed pain in my lower right adominal area before my period. I've had that sensation off and on all this month. I figured I should buy a pregancy test but i'm not sure that it would be a vaild point considering i'm not sure when my last period was. Before I became sexually active my period was usually at the end of the month, and moved to the middle and back to the end sort of. I believe that it may have extended or almost extended into the following month, I can't recall. I do have headaches often. I don't feel any more hungry than before, and nothing has changed in my day to day life. I guess what I'm asking is should I take a home pregnacy test? If so should I believe it? Or could this possibly be a health concern?