I am 17, 5'9, 143 lbs (healthy despite being about 10 pounds overweight) keep up an average diet, with the average exercise and I have very mild asthma. I have been on break from school since the 19 of December and have been relaxing. I have suddenly started experiencing frequently occurring head rushes when I stand up (for the past week or week and a half, give or take). When I stand up, black/purple spots entirely or nearly cover my vision, which then it takes me around 25 seconds to recover my sight and get over the dizziness. I used to experience head rushes like these last year (about last February, but I they have also occurred infrequently since then). I also have regular periods but I am around a week late now, though I have cramps and headaches. I have never missed or been late on my period before. I would also like to note that I have never had sex before, so pregnancy is definitely not the issue here. I was just curious if this could be pointing to anything underlying or if it is just my over reaction. Thank you.