I'm having a long term issue with my client

Whenever I load into a game, my cursor turns back into a regular desktop cursor, and if I don't switch screens to and from the game, at some point I'll right click and I'll be sent straight out of the game onto my desktop, and I'll have to click back, which sometimes can lead to me dying or being heavily punished while I can't see what's going on.

I tried uninstalling and reinstalling the game using the Hextech tool. Still happens. This started after some major windows update and I haven't found a fix since. I hesitated posting because sometimes when I post on a bug or problem, I never get a reply, but I just got a major error that kept me from playing a match because of this. I want it fixed.