What problem may I suffer from.?

Not anywhere near enough info to even make an educated guess. Sounds like you've spent way too much time being alone. When that happens, fantasies and es can get out of hand and consume you. Find something constructive to do! Also, why are you seeking a diagnosis and not help? It makes me doubt how seriously you're taking your situation if it is, in fact, that bad. How old are you? That's a major factor. The older you are, the more serious I would take your problem. Fear of going outside or the world around you is agoraphobia. Mood swings can be caused by depression or bipolar disorder, but the fact that it changes from day to night suggests depression. Ultraviolet rays cause your body to produce more dopamine, which puts you in a better mood. Don't sit around in the dark all night, get some florescent lights. They help. Best substitute for natural sunlight. You do not have multiple personalities! That's an extremely rare case where you actually become another person all together with no memory of being them. Also, a question I have for you is: What do you do for a living that you don't need to leave your house? Are you retired or rich?