There doesn't seem to be a clear matter, but I would think something is wrong with him emotionally. If I ask him why he gets paranoid about my driving, he'll say I'm a bad driver. If I ask why he's accusing me of being with his ex, it's because "my ex said you were".

Yeah, I'd definitely look for an MD. Whether or not he's going to accept that he needs one is another story. But if not, I may just have to find a way to cope and move forward.