Self assigned IP address?

Hi, I recently purchased a MacBook Pro. It works fine on other wifi networks except at my house. This is really starting to **** me off because the only way I can get on the Internet is via ethernet. Whenever I try to connect to my wifi it says "self assigned ip" I've tried using the ip address from the ethernet cable and putting that in manually as the IP for the wifi, which it then connects to the wifi network but will not connect to the Internet. The Internet is working fine on other devices such as my iPad though, so i know it isn't the router ( though i did try resetting it which did nothing). If it helps any, in network diagnostics, the light is green for wifi, wifi settings, and ISP. The light is yellow for network settings, and the lit is red for Internet and server. Please reply ASAP and thanks for any help (: