Extreme lag on multiplayer servers

So, when 1.6 came out i realized that with the new launcher i was unable to log in to any multiplayer servers without experiencing extreme lag and being disconnected within a few seconds. So, as a way around the lag i used magic launcher, which worked fine for any server and i had no problems with lag using it. Now when 1.7 came out i tried logging onto a server using the regular launcher (thinking the old issue would be fixed) but i am still having the same issue. So i figured i'd have to just keep using magic launcher, but not even magic launcher will work now. Every time i log onto a server it gives me the error message "Failed to log in: Invalid session (Try restarting your game)" and when i restart my game i am still given this message upon logging onto any server.