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Hi there. This is a fairly common constellation of signs and symptoms and may be very distressing, particularly in young persons such as yourself. While stress, anxiety, fatigue, etc can create these symptoms, an organic cause must be ruled out as far as possible. The normal CT, MRI and eye exams are very reassuring in this regard. I assume your blood tests have also been normal. Because many of these symptoms are variable, vague and non-specific you need to try to pin them down and measure them as far as possible. The best way to do this is to undergo neuropsychiatric testing. This is a battery of tests that tries to capture and better define the cognitive issues you are experiencing, including the memory problems. Once this is done, you should work with a neurologist and a psychologist to do any further testing suggested by the results, and develop a treatment plan that addresses these issues. You may need specialized blood tests or a lumbar puncture, for example. You might also need to get on a medication that mitigates the intensity of your symptoms without making you tired.
The CT and MRI merely rule out gross structural causes such as tumors, hydrocephalus, blood clots, etc. They typically do not reveal the cause or causes of cognitive issues. This would require neuropsych testing, which I recommend. Were your blood tests (e.g. electrolytes, CBC, thyroid, liver, kidney function) all normal? If so, you really have nothing to hang a diagnosis on. The neuropsych testing would reveal if there was some form of dementia going on. This would be very unusual at your age. More common would be what we call "pseudo-dementia" that looks exactly like dementia but is not really dementia, but rather a result of depression, anxiety and/or stress. If you successfully treat the depression or anxiety, the cognitive issues go away.
Ask your doctor for cognitive (neuropsych) testing. The results may be revealing. They may also be used as a baseline with which to compare any future testing that might be required, Definitely pursue the stress/anxiety treatment as this may be a cause or an aggravating factor. Either way, anxiety and stress feed into the symptoms and should be treated.
Other than the things already ruled out, the most common causes are stress/anxiety/fatigue, medications (going on or coming off), drug use, infections (untreated syphilis, Lyme disease) and occasionally an autoimmune disorder such as ME/CFS or a vasculitis.