[GAMEPLAY] Game Freezes and Lags Whenever Load into Summoner's Rift

I was having absolutely no issues until a couple of weeks ago. All of a sudden, anytime I tried to play a game, League would freeze every time I loaded onto base (whether it was because I loaded into the game or just because I had backed). Then it slowly transitioned to lagging when I was not at base and in time fights. Then it was at any given time in the game. The lag is so bad that the game is actually unplayable. I know it is not my internet because I have several friends who play on the exact same internet (both wired and wireless) and it works just fine. My computer can handle the graphics and the game as a whole and this is the only game that I have issues with. If it helps, the game causes the rest of my computer to lag as well as long as I have League pulled up still. However, the lag only takes affect when I am in game and not in pre-game lobby or loading into the game or on the main screen or anything like that. The issue is mostly limited to Summoner's Rift but issues can also be found in Howling Abyss, though just not nearly as bad. On Summoner's Rift the game is actually unplayable, while on the Howling Abyss it is somewhat playable (lags are mostly limited to team fights and backing). I have also tried uninstalling and reinstalling the game, and it has not remedied the issue.

Specs GPU: GeForce GTX 765M CPU: Intel(R) Core(TM) i7-4700MZ CPU @ 2.4GHz Memory: 12.00 GB RAM Current Resolution: 1920 x 1080, 60 GHz Driver Version: 358.50 Operating System: Microsoft Windows 8.1