If you have the WD hitch set up properly, it is not too tight. That is, the truck's front fender height is somewhere between 50-100 percent restored to unloaded height.
Regardless, the WD hitch adjustment will not cause sway.
Also, putting on a "sway control" device is NOT the solution!
The most likely cause, as others have said, is not enough weight in the front of the trailer.
Do you have bikes, or anything else, hanging off the back of the trailer? If so, take them off! They are causing your problem.
Where are your water tanks? If any of them are behind the axles, they should be empty when you travel.
You do NOT want to haul this trailer to the scales without taking some measures to cure the sway first.