Internet very slow and freezes / no threats on Malware

My computer is running very slow on the internet. It's Windows 7 Ultimate. I scanned it with Malware in safe mode and no threats popped up when I click on the internet it takes a long time to load and sometimes no pages appear at all. When I use the task manager the usage starts and 15% and jumps to 80%. And slows down. I don't know if it's popups or a hack or virus. I would just like it to go back to normal. Any help would be appreciated.