I have Comcast Xfinity and I cannot reach anywhere near my promised speed. My family desktop which is hardwired into the router reaches to 60Mbps and so do my parents computers and my brothers. I cannot seem to get anywhere close to it, I know with being wireless I won't reach it, but I should at least get somewhere close. I can only pull 6Mbps and thats terrible for what I should be receiving. Any clue what could be wrong here?

Edit: I have 100% signal and I'm not behind any walls