A Hitch receiver is that piece of steel with a 2" square hole mounted under your bumper. Pretty much all F150 hitch receivers have the 5000# weight carrying restriction. To tow anything more, Ford wants you to use a Weight Distribution Hitch in that hitch receiver.
You can also just mount a ball on your rear bumper and ignore the hitch receiver. That's a true bumper-mount and also limits you to ~5000# IIRC.
Anyway, your hitch receiver is not what's limiting your tow cpacity, assuming you use a Weight Distribution Hitch.
