in game lag

i've been playing for 3-4 years and after the last 2-3 patches my games been lagging out every game after my first match. I start off playing and going through a whole match without lagging, and then i start my second game and join in 1-2 mins late and start to lag after 5 mins where it jumps between 60 and 5 fps. I dont know what to do i tried all fps solutions that the game says and they havent worked. Any ideas?