I am 16 years old, when I wake up from my sleep I lose sight( my vision goes black this has been happening noticeably for about 2 weeks now) and recently my vision went black as well I lost control over my body and my knees started to shake and I almost fell. When this happened I completely lost control of what was happening that's why I really started to worry( it felt like a dream I remembered it but I remember that I couldn't do anything). This happened for about 5 seconds. After this happened I checked my bp and the only thing that was a little high was my SYS and it was 110 and my sugar was fine. I've started to drink a gallon a day since last month. It's summer so I don't move a lot I'm mostly on a chair for over 9 hours a day. I am not obese. I did cross country when I was in school. I don't drink soda or any sugary beverages. Only junk food I've been eating is ice cream and that's rarely and chips which I also eat that rarely. I'm around 138 lbs 5/9ft. I don't do drugs or drink alcohol. I don't go outside as well. I have not had any concessions or any injuries. I have read other post about people losing vision when standing up and they just had a bp problem. I've told my parents and they said the reason why this happens was because I'm on my computer all dam day. If anyone can help that would be great I'll appreciate any advice, if no one replies and it happens again I'll be seeking medical attention. Thank you for your time.