does anyone experience the same problem..? help!

soooo i started cf yesterday and nothing was weird or suspicious the frist moments. i've played like 2-5 minutes and then cf started to lagg very hard, i couldn't aim. so i pressed tab and saw that my fps dropped to like 20-30 fps...i don't know how this could happen because the day before it was all fine and i didn't download anything since then or changed settings. i tried the things everyone would do trying to fix this, redownloaded and reinstalled cf, updated my drivers and right now i'm running a virus scan. neither the reinstallation nor the driver update helped to fix that. would appreciate your help or suggestions. and sorry if my english isn't the best hehe