Inny, sometimes we get waterbugs here in the city... one will be here one moment, then gone the next. I am so scared of them that sometimes I get vivid anxiety images involving waterbugs.

As far as thinking you hear people coming in at night... possibly just a bad manifestation of your anxiety. This is something that regularly happens to me. I lose tons of sleep over it.

I'm sorry you feel crappy. Anxiety sucks.