I can't connect to my internet. I have a modem and a rouder, they show that everything is working fine, and I have my wireless adapter connected to my laptop. IT IS ON. I called my provider and they said that it's something wrong with the computer(idiots). But I went to town and had the same problem on my phone. In my connections, it doesn't even offer a wireless connection.

How did you verify they were actually working fine? This is important to know. On doesn't mean they are talking to each other. How did you configure them?

Did it ever work (is it new)... or did this happen after it had been working a long while?

I would suspect the configuration of your router or access point or the PC. Without more information like your modem and router configurations it is hard to tell.
What are the modem and router
IP Address
Subnet mask
Is SSID on and if so what is the name (you may want to change this from the default)
Also is security enabled