Sway Control

should help, a single axle is always going to be a bit less stable but should be manageable. what trailer, what tow vehicle and what hitch? also whats your tongue weight percentage?

it is a 2019 Catalina Summit 172BHS and I am towing it with a 2017 chevrolet colorado. not too sure of the tongue weight.

good starting point would be to head for the scales and get your real world numbers. the tongue should have roughly 13 percent of the trailers real world loaded weight. going to 15 percent wont hurt and will likely help with the sway.

also make sure tire pressure is correct at all 6 wheels

Load tongue weight heavier. With the light weight tow vehicle it's never going to be perfect. Air your back tires up all the way to the pressure on the sidewall.

Make sure you have between 400 and 600 lbs of hitch weight for that TT.
Shortening the ball mount (to reduce rear overhang distance) can help a bit.
Make sure tires are aired up to max cold sidewall pressure. If P tires, switching to LT tires (stiffer sidewalls) with a lower profile could reduce side to side tire squirm.
The sway bar can help, but if it gets wet in rain the friction is reduced. And when backing up it must be loosened or it can get bent. I prefer a WD hitch with sway control built in, like for example Equal-i-zer or Andersen No-Sway.

Sway bars will help but your'e pulling a 17' TT with a Chevy Colorado. Any light truck pulling a TT will be like the tail wagging the dog. Do what you can but short of getting a bigger truck (the right tool) you will be trying to play catch up. It won't be as comfortable as pulling it with a heavier truck. It's just the nature of the beast. Good luck

Your Colorado is certainly capable of towing that small of a TT. I'd look at the hitch setup. Make sure it is returning the front end to the original ride height. Also check the tongue weight. If it is too light in the tongue, you'll never get it to tow well.

how do i add weight to the tongue if need be?

Take stuff from the back of the trailer and move it to the front. how you load a trailer has a lot to do with it. get to a weigh scale and get real world numbers first. loaded trailer weight as well as tongue weight.