I admire your concern about your boyfriend. But while I have some ideas about what might be going on, it isn’t possible to make a diagnosis in this manner. What I will say is that you are right to have a concern. My encouragement is to suggest he get an evaluation by a psychiatrist or to have some testing by a psychologist, preferably one with experience in neuropsychology. Only in this way can an accurate diagnosis and recommendation for treatment be made.
Until then, protect yourself by not allowing his needs to eclipse your own. Be clear about setting boundaries, and make the suggestion for an evaluation. But most importantly don’t lose yourself in the effort to help him. Ultimately he has to want the change to take place, and that is something he has to do on his own.