Is someone able to take control of my computer?

You should run virus scans from a few different companies with fully up to date definitions. One of the things hackers love to do is create programs that "dial home" to their computers and relay commands from their control program to yours. They then encrypt the program and find a way to sneak it onto you computer, often disguising it as something else, or part of another program. There are constantly new encryption algorithms coming out for these things, and the anti-virus companies have to actually get ahold of one before they can program a way to search for it. I have seen these programs do pretty much anything the hacker wants, from watching through your webcam, listening on your microphone, to running any programs as if the hacker was sitting right at your computer, and because they are made to connect from your computer to them, they easily bypass your firewall.