Minecraft suddenly lagging

Ive tried gamebooster like 2 months ago, it seemed like it didnt do much. and i didnt download anything before it went bad.

You shouldn't mess with your settings right away if it was working before....
How are your temperatures? Check them first. You didn't download anything
right before it ran this bad? And you should also do what XxxAziexxX said.
After that check your hardware for any conlicts. If all is good, only then you start
changing settings. And there is always system restore if you have it enabled...

Defrag does not help alot, you should do it but it would probably help a little bit depending on how full your HDD is, it can take time also, around 1-2 hours+.
I would also recommend downloading Razer Game Booster 3, you can boost any game you have and I would say it helps quite a bit, If none of that helps go on the Nvidia Control Panel (If you have an Nvidia Graphics Card) try restoring the settings on the 3D settings tab

My computers fine. I already have optifine and does defragging help a lot?

Open you task manager and close any redundant or unused programs running in the background. If you have anti-virus, try running a virus scan. Also, if you have anything to clean/de-frag your computer, try that also. Also, if your computer was left on while you were away, try a restart.

Get the Optifine mod.
It should help some.
I believe Mojang is optimizing the game more in the 1.5 - Redstone Update.

bad computer?