well,,, if I'm honest I would have to say that he's not doing a great deal to put your mind at rest.
There are keyloggers available that enable you to find out what anyone is doing on a computer, they're often sold as a means for parents to spy on thier kids.
My only real advice would be (assuming guilt) ,kick him out on his arse.
I live by the rule of never accepting less than I believe I'm worth.
Sounds like it's time for you to do some serious weighing up , don't sell yourself short, only you can make the decisions that shape your future.
Good luck :thumbsup: