Minecraft lagging after awhile?

So I recently re-installed my OS due to a weird corruption it had… Anyways, but ever since that Minecraft has been acting very weird, basically I'll play the game lagless for about 10-15 minutes then suddenly the FPS drops from like 60 to 0… And it won't stop, and it only gets worse and worse and worse! Sometimes restarting Minecraft helps, sometimes it doesn't. And I don't understand what the problem is. Here's my specs:

CPU: Intel i5 2500K
GPU: Nvidia GTX 560 TI
RAM: 8GB G.skill 1333Mhz
OS: Windows 7 Home Premium 64-BIT

I have Java 64-BIT installed, I've tried allocating more RAM to the game but it doesn't help. Looking at the performance tab in Task manager, my CPU/RAM doesn't go up during the time this happens so I don't think they're the cause, I don't know what's wrong. Can anyone help? This is annoying… I've tried doing some googling but nothings working!

I think it's best that you try formatting your computer again and re-install Windows again. After that, install all the latest drivers and hopefully it will help.

I know it's annoying, but I've seen this work on my own computer. If that doesn't work for you though, then I do apologize for wasting your time on resetting everything up again.