100% graphic card usage in game and low fps

When 8.14 hit live league started to use 100% of my graphic card and my fps dropped from 120 to 36 and it feels really laggy , when i alt+tab it uses only like 10% and graphic options doesn't doing anything, but if i change my resolution to 800x600 then my fps increase to 70-80. Every other game like overwatch, poe, witcher 3 works fine. I tried everything, i did everything from support fps increase page, i turned off everything in windows 10, i revert windows 10 updates, i reinstalled the game, i used troubleshoot thing, i update my drivers, i updated my bios, but nothing happened. BUT when 8.15 hit live my fps revert to normal state for like 2-3 days and then dropped again. And league support doesn't give me much help Please help.{{sticker:sg-soraka}} Card name: AMD Radeon HD 7800 Series Processor: AMD FX(tm)-8120 Eight-Core Processor (8 CPUs), ~3.1GHz System Manufacturer: Gigabyte Technology Co., Ltd. System Model: GA-970A-DS3
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