Q: Keep getting Disconnected every 30-40 seconds?

So I have a Macbook Air 13" and is the early 2014 version. So everything was going fine until I woke up the next morning and its like that. I kept getting disconnected from the Wifi every 30-40 seconds. And everytime I try to reconnect, 30 seconds later it gets disconnected. After that, I tried to forget the network and now I am unable to join. Can someone help me with this please? I was downloading OS X Yosemite but then I paused it and left it there for a few days. After that I deleted Yosemite, restart the computer, turned off the keychain, reset the PRAM, deleted System Configuration, set wifi service order, but it still the same. Someone help me ASAP please