Is it sway or wiggle? Sway is defined as the rear end of the trailer oscillating side to side with increasing speed and distance of oscillation. Is the rear end doing it or the whole unit moving as one? Or are you having more of a porpoising movement front to back?
More info is needed... what is tv (yr, make, model engine, rear end and 4wd/2wd), what hitch do you have (what is wdh rated for, any sway bars or is it an integrated hitch like Reese dual cam, equal-i-zer etc)? Have you been to the scales to weigh anything? This is very telling. What tires on TV (P rated, E rated) and what pressure are tv and tt tires running at?
Sway can be from too light of a tongue weight and too heavy on the rear end (I have moved a tent that weighs less than 20lbs from the back to the front and made a big difference in handling before). Too soft a tire on the tv (ie p rated tire or under inflated E rated tire) can have a negative impact on towing. WDH not adjusted properly can negatively impact as well... not enough weight transfer or too much transfer are both bad (you can tell by measuring height but also a more accurate method involves weighing at a cat scale). Not enough tow vehicle (especially with a short wheel base) can be bad too.... how do I know that? Been there done that with my old armada my friend.
2014 Crew Cab Chevy Silverado 3500 4wd Duramax/Allison
2014 Sabre 34REQS-6