MacBook Pro wifi connection is failed.

I got a problem about my MacBook Pro. I try all the option except change the wifi card. The problem is the wifi bar is pop up in my laptop but I can’t connect to my internet. I have other devices which is connected my home internet except my MacBook Pro. I don’t understand what’s the problem? Sometime it is connected for 5 minutes but the signal is very poor. The router is very close to my laptop. Please let me know what’s the problem? Thanks in advance.