Every time I get on a server or a single player world, I get about 30 fps but when i walk, i teleport around pretty much. i wont move for a few seconds and it will just teleport me like 3 blocks forward. I dont have any mods and i have fast internet, this even happens on single player worlds. But I have a kind of slow computer so I dont know if that is the problem
It is probably your system to blame then.
Make sure your system time is correct, otherwise your computer may not be able to handle Minecraft, try closing any other applications running.