Have I been hacked?

I decided to use the command uptime just for the hell of it and saw that there was 3 users logged in on my system. I knew I was logged in as root on one terminal and I was also logged in as another user on a different terminal.....so who was the 3rd user?

This is a fresh install and if it sounds fishy to you guys then I will just reinstall just to be perfectly safe.

Use the "w" or "who" command to see who's logged in and from where.

I think I may have found out what it was. When you start up the desktop using the startx command I think it logs you in again under the same user that you typed the startx command with. I got the same results again but only after I had the graphical desktop up and I had my firewall script up this time too. Its kinda strange because I dont know weather to feel stupid that I may be over reacting or worried because I may be correct about being hacked lol.

is the third user always logged on? or logged on under certain conditions? or does it just randomly appear?