My ping is high, mouse is stuttering, and audio is stuttering. Perfect internet.

Just got done playing a perfectly normal game of league. I go to hop into the next game and i notice that for some reason while loading into the game that my brightness randomly turned up. I try to turn it down but it won't work. Then when i get into the game, i have high ping with perfect xfinity internet and an ethernet cable plugged into my laptop. Also, my mouse is lagging with the game, so if my ping jumps up, so does the lagginess of my mouse. Also my ping only jumps up when there is a lot going on on my screen. It's almost like my fps should be dropping but instead my ping is jumping, along with audio stutters and mouse stutters. HELP ME PLS