http://steamcommunity.com/id/umpkin/games?tab=recent
looks like he/she has been playing CSS unless you managed to get in 60 hours worth of gaming within a day

. Also it says you hae 150 hours total for CSS so going on average times he's racked up, he can't have had your account for that long, well, maybe a couple months? So won't be too likely you have VAC bans.
Also i'm willing to bet that this isn;t your group...
designers by KRIT&REVKA
http://steamcommunity.com/groups/psrevka
Your the only one in that group and if it's not yours, try checking to see if you can see who quit and joined it, cos it may give you clues. By googling i can see someone called Squizz used to be in that group but isn't anymore, but he might have been another hacked person.
Also rejoin the CiC group
finally. get on mumble and rejoin all the CiC crap, and buy minecraft
