MacBook Air won't connect to Wifi

I recently got a MacBook Air everything seemed to work just fine, but a couple of days ago it stoped been connected to the Wifi, at first it connected and disconnected almost every 2 minutes to eventually not been able to connect to the Wifi. I tried reseting it, in hopes of fixing the problem but it didn't work, then I tried running a wireless diagnostics which showed a few issues (Review Wifi Best Practises, Wifi Not Associated, Conflicting Country Codes, and Poor Wireless Environment). I don't know what is the problem I only use my Mac for researching and doing assignments online plus I have my iPhone connected to the wifi and has never had a problem. Can someone please help?!