Hi My Boyfriend Is 43 And Last November Got Real

Hi my boyfriend is 43 and last November got real upset over his father dying. He cried for about an hour or two and after that he started stuttering. He started stuttering again last month so we took him to the er on a Saturday and they kept him until that Monday They did a ctscan and MRI and nothing showed up He went to a neurologist and had a seizure while there. Still no answers. He had a seizure again at work this last Tuesday and was taken to the hospital and they ran tests but still nothing shows up. His legs get weak and he sleeps a lot more lately. One minute he is talking fine and then the next he is stuttering and feeling weird. What is this?