Minecraft Unplayable. Crashes and whites flashes?

Okay so This problem with minecraft has been slowly getting worse. It started when I was playing there was these white flashes coming on my screen. It didn't seem to affect the gameplay just really annoying. Then I was trying to break blocks and after a few seconds the block would come back in the same place. I have a decent computer and it's played high end games pretty good. The fame still slows down to 15 FPS and it's really starting to piss me off. I just want to know what's happening and if I can fix it. Also adding to the problems sometimes when the world tries to load the whole game crashes and I have to reset my PC to fix it.

First have the computer check for bad sectors and bad files, depending on your OS the checking is done differently. Find out how to do it on your OS's website. After the checking is done defrag the drive and check for any updates for drivers. I know for Windows there's Slimdrivers, it is a free software and does have a paid version that will update drivers automatically. Once all this is done check the game again.

I'm sorry for your loss. The toasters in your computer seem to be burned.