I have some similar anxieties; I constantly worry that someone is there, forcing me to compulsively search around. I know that nobody is actually there, but I still seem to hypothesize that this or that might happen (someone's in the apartment and they are going to do something awful) Of course, even after searching around and proving that no one is there, my anxiety doesn't usually lessen... I'm still struggling with this issue, but I've developed a few strategies that have personally helped me at least a little:

- If you have someone that knows about and understands these anxieties, talk to them about them when you can. Sometimes it's helpful to find someone that can reinforce your understanding that your anxieties are not a realistic assessment of the situation (nothing is in the house, in the closet, etc)
- This may only work for me, so only do it if it applies to you (don't do it if it will make things worse for you specifically)... When I'm alone in a dark room with no noise going on (working on the computer, for instance), I find that turning on the TV and some lights can help. Having the noise can simulate the sensation of (pleasant) company. Lights reduce the sense that something is hiding in that dark corner, as it's easy to see what's going on around me.
- I find that just calling someone, anyone, about anything at all can help. Meaning, I might call a friend and ask them how things have been. The conversation helps get my mind off of my worries.

I don't know if any of this will help you, but regardless, you should definitely do what the above poster suggested - talk to your therapist, if you have one, about this. Best wishes, and I hope you find some good strategies to manage these anxieties. I know it's not easy.