Someone is accessing my machine

You may have "disabled remote access" -- except for whatever back doors an intruder has opened. Take it off the web yesterday.

It is my humble opinion that the only recourse when your machine has been compromised (assuming your description is accurate, it surely has) is euthanasia, followed by putting the dead carcass on a pyre. Nuke it hard and start over. That is the only option I would consider. You simply cannot trust that you can find every evil thing in every coer and remove it.

I'm sure you have been keeping regular backups of your important data, have you not?

Do you have a roommate, by chance?