(adsbygoogle = window.adsbygoogle || []).push({}); This only happened today. I launched minecraft and wanted to finish my roof on single player, blah, blah. Anyway. I lagged really bad and only got like 8 fps. I normally get like 28-35 fps.

I didn't do anything unusual. I didn't have any programs open. It froze and I had to close it with task manager. This has happened 4 times in 20 minutes now.

clean up junk files
raise your RAM for minecraft using task manager
defrag your system
reinstall minecraft
reinstall java
delete non permanent information for minecraft
A reliable windows registry repair program could also do the trick

This should help, personally I just had to reinstall minecraft and I was good to go again

If I reinstall minecraft, do I have to start a new world?

backup your file for that world and paste it into your new minecraft install folder

Thanks Cammmmy. btw, you weren't on holiday at the start of the month were you? (Stupid question but someone in my hotel was called Cammy and used ngu)

OK and oops..