My last question- if I had a MRI of my brain with the dye, would this rule out dementia? 19 male, have severe confusion/memory loss/depersonalization

You do not have . Dementia. It is possible that an MRI with die could find something else that is causing your symptoms, but it is impossible to have dementia of the alzheimer's type at your age. In fact it's highly unlikely that you would have dementia of any kind at your age. The fact that you have confusion, memory loss, and depersonalization, all make me wonder if you do not have some form of dissociative disorder secondary to trauma. You could also have that combination from temporal lobe epilepsy. Sleep apnea can cause cognitive deficits as well. Please see the finest neurologist available in your region for a thorough checkup. If nothing comes from that then see the finest psychiatrist in your region that you possibly can.Share with them some of the thoughts that i've shared with you.
Not dementia. At the age of 19, it's far more likely that these symptoms are due to a psychiatric condition such as depression than to dementia. Talk to your doctor. Mris can't rule out dementia.