Speaking as a person who has a life-long, frequent history of seizures, I can say that I've NEVER had a seizure in which God, or anyone else, spoke through me.. Your ex most likely has a seizure disorder, and when he tries to speak, it comes out sounding garbled. That is because the brain is suffering a sort of "crossed wires" during the seizure and it takes quite awhile for the speech pattern to go back to normal. Sometimes I can't speak a coherent sentence for a full hour after some of my seizures, depending on how bad they are.. :/ God doesn't use seizures to speak through someone, I guarantee that.
You need to leave your ex alone, you need to get all this doubt out of your head or you'll NEVER hear God's voice. Tell your ex to go to a doctor and get diagnosed, and then take yourself to church and talk to a pastor.