lag the moment i move and/or enter lane. otherwise everything is fine.

so i was playing a game and everything went A-OK, champ select went smooth, login went smooth, but as soon as the game starts, i move 1! yes, 1! step and my ping spikes up to 600 ping+. i have windows 8 and idk if it has anything to do with it, but does anyone else have this problem? or is it just my internet? my brother is playing in his room on windows 7 and everything (even ping) is fine for him. why is this only affecting me?