I dont know what pcos is but taking that out... it could be that you had just waken up and eaten ... . try at night.. but you shouldnt stay the whole day with only a soda and 3 cookies that is not healthy.. why don't you try to eat fruits b/c they have a lot of sugar ..like strawberries, orangers, and so on.. if it continues.. then go to your doctor.. . and the only reason you fainted was b/c you saw blood so your doctor is right and he had the blood tests so don't worry.. he would tell you if something is wrong..also talk to your mom and see what she thinks... maybe your sisters thing is not working right?. it could be... but don't stress over it.. just eat right ....b/c you are not feeling anything..