Is it possible i have alzheimer's? i'm about to turn 19, memory is fogged, feel pressure and sensations in head, no concept of time. no sleep, scared

No: While there are familial cases of early onset alzheimer's disease, they don't usually present in their teens. Given your symptoms, it's best to go see your family doc for a complete evaluation. You've listed 3 things that really need to be monitored by your family doc: oxygen, high blood pressure ; post traumatic stress disorder. This should be monitored by your psychiatrist, too.

Not likely: But with your symptoms you should have a complete check up to find out the cause of your symptoms.It all may be related to your sleep deprivation or not proper nutrition and other life style factors or some obscure medical condition.Go get it checked.You are 18 and ask your parents to take you to family doctor or the pediatrician.

NOT possible but...: No, it is not possible- alzheimer's usually begins in one's 60's ; never occurs before 40's, but there can be many other reasons for your symptoms including hypothyroidism, lead, mercury or other heavy metal toxicity, other environmental toxins, infections such as lyme disease, deficiency of vit B12 or other vitamins, side effects of meds as well as severe anxiety or depression. See a good doctor.