i'm 18 too, female, and i have the same kind of symptoms
i'm also quite a hypocondryac too, but this feels different, and i'm certain it can't be anxiety making me feel like this because half the time i don't feel anxious, i just feel wierd. i've been getting pressure behind my eyes, more on my left eye, and a dull kindof ache on the left side of my head, but its not really a pain. my vision seems wierd, like not blurry but it doesn't seem right, and i get little flashes of light or lines?
i've also had chest pains but the doctors have checked my heart and done a blood test to rule out thyroid etc and it was all fine. do you ever get cold hands or a cold nose too? i keep getting that.
i get really strange lightheadedness, although my head isnt really LIGHT its more like i feel im in abit of a dream, like its not my body, and if im standing still itll feel like im swaying or about to fall over but i'm not. it's so wierd :/ i also got a mild heatrash (thats what the chemist said it looked like) on my hands but that might be something completely different, it seemed to come since i took an ibeprofen so probably that. i'm going to the opticians first, theyll be able to tell if it's my eyes and if theres any pressure. it it doesnt go in a week or so i'll go to my GP again. have you taken drugs before? or recently? i did quite often about a month and a half ago but ive stopped now. if so it might be a side effect from that. x