Getting really weird FPS issues! Please help.

Hi, I'm getting around 25fps down from 140fps usually. I play with all settings on low apart from high texture, high effects and medium shadows. Some games of dota its at 140 other games its as 25. My specs are:

http://imgur.com/a/59gVk

i5 / gtx 750 / 8gb RAM. Only that that changed was that i upgraded to windows 10. Please help! and thank you!