I have always had a real problem with sleeping overnight on my own without anyone else in the house. When I was at uni, when I was single and my flatmates were staying out at their boyfriends' houses, and later when DH was away on business (which he was quite a lot).
I could just about handle it when I was on my own, at least I could always go and stay with a friend etc... If it got too much. I just turn into a gibbering wreck, scared at the slightest noise, sleep with several telephones, the bedroom door locked, and generally get no sleep at all because I feel so vulnerable, I can't nod off.
I hate hate hate it, because otherwise I am usually a very strong person. I feel like such a baby, and now I am faced with DH having to do more international travel with his work. Now I have DCs and the baby is awake several times a night - I feel terrified with the responsibility, and being alone walking around in the dark with a teething DD. This is causing arguments - am I the only one who feels like this? Also the MIL is aware and thinks I am being 'ridiculous' which is further fanning the flames as i feel no one understands the terror I go through.