Internet speed drops from 172mbps to under 3mbps

Hello,

I have clocked my internet on my mac book pro and it comes in at 172mbps, even though my plan is for 150mbps with Cox Communications. When I play online, Xbox One or Xbox 360, my connection only clocks at between 2 and 3 mbps. I am running it on the same Ethernet cable and cannot figure out why there is such a big drop. I can't get more than 3 bars on any online games and it is frustrating, considering I have an incredibly fast connection that isn't working. It lags with all games and apps, Netflix, COD, Hulu, MLB... they all lag. Any advice you could offer would be greatly appreciated.

Thank you,

Dan