That's strange.
I think it's important for you to take the laptop to a friend's home; a relative's home or a public wifi hotspot and test the system - see if it stays connected to the Internet.
If not, I would then recommend that you reinstall Windows to see if the wifi works after a fresh Windows installation.
If the wifi doesn't work after a fresh install and you have ruled out the ISP, including the modem & router, then you'll need to bring the system to a PC repair shop to be looked at because at that point in time (after all of the other steps check out), the cause would likely be hardware failure of the Intel wifi card.
You can either do that or purchase an external USB wifi adapter for $30-$50 and use it for your wifi device.
We have now covered everything that I can think of.
Regards. . .
John