Someone may be able to suggest something better, or correct what I’m about to say, but try Winmrt. Run a trace to something like google, or indeed to the server you’re playing on. If you notice a spike in your ping or package loss to the router, then it’s probably your wireless, beyond that is probably internet. I’m not sure what results you would get from someone else downloading though, but I’m sure if you post the results here someone can interpret.