Why is my connection so terrible?

My game is always insanely choppy and constantly lagging. It has become completely unbearable. I don't know why it chooses to control like I have a lead sheet over my entire room blocking all internet. I turned off usage sharing as I heard that might help, but it didn't. I have friends with weaker computers and worse internets that run it just fine (though it's not a computer performance issue, it's a connection issue). No other game I've recently played has this problem. how fix? I'd be having so much fun but it feels like the game doesn't want me to play it.