my xbox internet is acting up and i don't know how to fix it

i've tried restarting my console, i've restarting my router, i've done every trouble shooting thing and my download wont go up i've checked it through xbox and its sitting at 280 but when i download something it drops to 5. there is not many people on the internet and i downloaded something earlier and it was fine but it just started. any ideas whats going on?