Weird scratching sounds? Maybe ghost?

Okay, so say it's time for me to go to sleep. I turn off my lights, get's all cozy, lay on my side and put my head on my pillow. Few seconds later I hear scratching. Sounding like it's coming from under my bed. Which is impossible, nothing can get under there, PLUS I have a thick mattress. But the scratching never fails to stop. Sometimes, if I put my hand over the scratching I can feel it. Other times I scratch back, and then the scratching speeds up. Even if I turn on my light all I can hear the is the constant scratching coming from...well, under my bed. I know it isn't bed bugs or anything like that. Because even with my old mattress I heard scratching sounds. I feel like a lunatic. I moved to another house later on....the scratching is STILL occurring. What is it? It's not my cat. I'm almost starting to consider a ghost. The scratching mostly occurs when I'm on my bed, but I've had many cases where I lay down on the couch and hear it too. Right beneath me. Sometimes when I stand I feel it under my feet. I don't even have to be at home, one time it happened when I was at church! By the way: I have had more than one mattress and more than one house. It isn't any form of rodent, this I am positive of. But, that doesn't help me know what it is. Help me please, I can't sleep through it. It freaks me out so much...thanks. -Val