Fiance gets extremely moody before going to sleep, what to do?

My fiance is the kind of guy that gets very very moody before he goes to sleep. But you cannot tell when its gonna happen. One minute he's fine, then the next he's snapping at you. My fiance and I have been dating for 2 years and he's a moody person in general. But it gets to be hurtful when you can't tell when hes gonna get mad and snap at you before bedtime. Tonight before he went to sleep I held his hand and told him I loved him, that there was no one else for me, and that I pictured us growing old together. I asked him if he could picture us growing old together and he said, "No, because I can't even get to sleep." It hurt, bad. Then he seemed a little okay before he went to sleep a few minutes later. He goes to sleep very quickly. I don't bother him alot before he goes to sleep, so its not like im keeping him from sleeping, hes just so snappish at that time. Dr. Jekyl, Mr. Hyde. But when he's asleep, if he hears me make a noise he wakes up and asks if im ok, and if he feels me brush up against him, he'll rub my leg or place his hand on my foot. Then in the morning when he wakes up, hes very moody again til hes more awake. I dont know what to do. How should I handle this?