internet ONLY goes out when playing league

So my internet got changed about a month ago, and ever since then it's been cutting out causing me to dc for about 30 seconds in league, at first I just thought the internet was wonky because it was changed, but recently I pinpointed it to league itself.

My speed is 100 mbps, it runs flawlessly everywhere... except for when I'm in league. When I'm loading in to the game and watching youtube or twitch to wait its buffering constantly. I dc almost twice a game usually, I can't play ranked because it's too risky to do.

If anyone can post a fix or see what my problem is please do

-fatcat3000