Call of Duty problems

Hello,

I wound up getting a virus and had to set my computer back a week, after i set it back everything seemed to be working great, bought a virus program, no more virus. Now whenever i try to play CoD online it wont let me get into games for team death-match..etc...it says im in a server but cannot find a game, i have, however, managed to get into a few free for all matches online, weird.. i also cannot join friends games, or invites, from steam. Im not really sure what the problem is or how to fix it, I dont want to reinstall the game and loose all my progress. If anyone can help itd be greatly appreciated!