From reading the OP's posts, and the replies, I have to agree, not enough tongue weight.
A properly built, properly loaded trailer should not sway. If it does, there is a problem with the trailer. Find out what the problem is, fix it, and THEN, if you feel a super duper fancy high-tech hitch or sway control is necessary, use it. But, please, don't rely on that hitch to actually FIX the problem. It won't. Oh, yes, it may cover the problem nicely, giving you a false sense of security, but it will not FIX anything!
Remember, you want the tongue weight to be 10 to 15% of the total weight of the trailer. The heavier (and larger) the trailer, the closer you need to be to 15%, IMO.
I see 30 to 35 foot enclosed cargo trailers a lot around here. I have yet to see one with a WD hitch or sway control. Yet, they have no sway, even at freeway speeds. I wonder why? Maybe it is because they are built with the axles about 2/3 of the way back, and they are loaded tongue heavy.
To the OP, take your rig to the scales, weigh it, and load the trailer so that you have 13 to 15% of the gross weight on the tongue, and I think your sway problem will go away.