Terrible Internet

Hi, For about over a month now i have been continuesly getting disconnected from the internet anytime i actively use something (I.E: When i play my MMORPG online and do anything productive in game). It doesnt disconnect much if i am not doing anything active on my computer. I have restarted my modem and restarted my router, i have made sure all the cables are connected where they should be and are secure, and i have even done virus checks to make sure its not that. I have no idea what the problem is. I have contacted my internet provider to see whats up and they say that everything is working fine, they even sent over a tech and he said everything was fine. What do i do? This has become really bothersome to me and my housemates! Also when i try to repair my connection, it says this: "Windows could not finish repairing the problem because the following action could not be completed: Clearing the DNS cache." Im also not sure what that means. Can you help? D:

When you mention your housemates, is that suggesting that they have their own computers and that they too can not maintain a reliable connection? Or, is this problem specific to one computer?

No they all have their own computers and cannot keep stable internet. I have a router that gives off wifi to them and they have been disconnecting alot also. I checked the router and updated its firmware and its completely fine and updated.