Is anyone else but you using your internet? Because if there are more internet users, the chances will be less of your internet of becoming as fast as it usually is.
If it is not that, then it is because you have many apps going on during the duration of using your internet. Your computer might not be responsive as quick because of this. Close all the apps from the RAM (This, you can see from the bottom right icons. Simply put the cursor over an icon, right click, then press quit/exit/abort. Or, you can do this another way by ctrl+alt+delete, then go to the processes tab, and quit any apps/programs that you think are not needed at that time of use.)
If it is not that either, than there might be viruses that makes your computer + internet to slow down. Get a Virus Program to resolve that problem.
Thanks!