Strong internet connection but no internet

hello guys, recently my internet on my computer has been acting up. When I switch on the computer and start using the internet, it is fine. However 5 minutes later and it goes. But the router still shows strong connection. Once the internet stops working on my computer, all my other devices (ipads, phones...) internet goes. It comes on for about 5 seconds here and there. But that is no use. Could someone please help me? Windows 7 DELL computer intel icore7. If you need more information just ask me. THANKYOU VERY VERY MUCH