Is there such thing as TIA memory loss?
It sounds like you could have a serious condition, and based on what you are telling me, I think you need to get yourself to a large, tertiary, Neurology clinic for evaluation, and soon.
Having a "TIA" at age 21is highly unusual. At that age, you should have been seen by a stroke specialist for that diagnosis to have been made. A search for clotting disorders, heart defects, and genetic stroke diseases should have been undertaken. In addition, a TIA, by definition, leaves no lasting damage, so it cannot be the cause of your current situation. Either you have had multiple other events over the years, or the diagnosis is not correct.
In either case, it sounds like you need an MRI of the brain with contrast to find out what the brain looks like. In addition, you will likely need blood tests, possible lumbar puncture for cerebrospinal fluid sampling, and possibly genetic tests for Neurological diseases of the young.
In summary, you need to get to a tertiary Neurology center right away. There is a good chance that whatever you have is treatable, and needs to be evaluated soon before additional damage is done. Your problem may be stroke related, but it may not, and needs to be evaluated carefully.
