This is really a tough one. You can't argue him out of his delusions. They're not based on logic, so reasoning them away is impossible. You'll only exhaust yourself trying.

Basically, if you're not planning to leave him, then you have to stop constantly reassuring him. And, when he wants you to swear you'll never leave him again, you have to not do that. Because any oath you take will never be good enough. Best to say: "I don't plan on leaving, and I don't want to, but it's possible you could drive me away. I can only withstand so much." When he starts, remind him of the promises he made to lure you back.

He might be helped by a very good therapist, if he can be persuaded that this is a sickness. This is similar to a kid throwing tantrums, only it's more like incessant whining. It's meant to get a response out of you. Don't give the expected response. That reinforces the behavior. Do not walk on eggshells and do not curtail your behavior to try to avoid triggering one of his "spells." That just causes him to get worse. What will appease him short-term will only make him worse long-term.

To some extent this is like an OCD behavior that he truly can't turn off. He has to be made to understand that you are sorry he experiences this discomfort when he feels untrusting, but he'll have to learn that experiencing some psychic discomfort is not the end of the world and will not kill him. Your instinct to reassure him is not serving you well. Watch Cesar Milan - the dog whisperer, working with whiny dogs. You ignore the behavior that you don't want. Your husband needs to learn to self-soothe, and he can.

His distress is not imaginary. It's real. But resolving it is his problem. You have to be very firm and willing to bestow affection and approval when the whining is not going on.

Some evening, when he is not acting delusional, you hug him and say, "See how nice we are together when you have your head clear of wrong thinking. I love you when you're this way. I'm proud of you when you are thinking straight."

He is insecure. Then you become insecure, which makes him more insecure. You have to be the strong, secure one . . . unruffled by his carrying on. That's really what he wants, but he doesn't know that.