Please read up on proper trailer loading. I was almost one of the horror stories.

My prior TV was a GMC Safari (Chevy Astro Clone) and at the time I had a 21' dual axle travel trailer. I knew I was close to the limit of the TV capacity, so I loaded as much weight as possible at the rear of the trailer to take some weight off the back of the van and BIG MISTAKE!!. We're loaded for a long camping trip with everything we could fit in the trailer, when we were passed by a pickup truck while going uphill. Trailer started to sway severely and shake the van, to the point that I almost went off the side of the road. The trailer sway was so sever that ALL FOUR TRAILER HUBCAPS flew off. I knew enough to not slam the van brakes and to apply the trailer brakes independently to gain control. Other than almost filling my shorts, losing the hubcaps, and opening all the cupboards in the trailer nothing happened.
After the trip, I researched and researched to what I did wrong. I was using a Reese Dual Cam sway control with load equalizing hitch, but that could not make up for my mistake of overloading the trailer and placing too much weight in the rear and causing the tongue weight to be too low.

I learned to:
Load lighter
Weigh the trailer
Have proper tongue weight (12-15%) (I purchased a Sherline tongue scale)
Drive slower
Get a better tow vehicle (Like an Expedition EL

I have other posts about my travel trailer experience and setup, but you shouldn’t have a problem if you’re loaded and adjusted correctly. I highly recommend the Reese Dual cam Sway control with Load Equalizing hitch, and the Tekonsha Prodigy electric brake controller.

03 SVT VERT had some great comments about making sure your trailer is OK first a competent trailer shop may help identify some underlying issues.