I've ran into a problem hoping maybe someone can help. Here it is..

I just switched internet providers this past summer. I have a desktop computer & a laptop. They are both wireless, but the problem is I can only use one or the other. I am not able to use both at the same time. Same with xbox live..I have to choose between xbox or computer I'm not able to use both at the same time. I get a message that says IP conflict. My assumption is that the router does work because I'm getting a connection..just not to both. I called my internet provider & they said I should be able to connect more than one computer. They told me it was my router....So I reset the router, turned everything off, waited a couple minutes. Still nothing. I have no idea what to do??? Do I need a new router?? I have no idea, but I want this fixed

Anyone have any ideas??