First of all, keep in mind that I am unable to diagnose you because I am unable to examine you, this forum is for educational purposes. The symptoms you describe are most consistent with depression. The classic symptoms of depression are of sleep disorder, anhedonia (not taking pleasure in your activities), feeling of guilt, decreased energy, problems concentrating, changes in appetite, and thoughts of suicide. However, depression can present as more minor symptoms such as lack of "feeling like yourself", and/or memory/cognitive problems. I would recommend that you have your neurologist order formal neuro-psych testing. This can help differentiate between an aphasia (cognitive speech problem) and depression. I would also recommend a trial on a SSRI (such as Lexapro 10mg daily). Remember you do not have to "feel depressed" to be suffering from the effects of depression. If your Neuro-psych testing reveals signs of an aphasia, I would recommend an MRI of your brain. I hope this has been helpful.
Have you given any thought to depression? You seem to have fine thought processes based upon your letter. I have had two major depressions ( many years ago ) and a major depression will have this feature often.