Bev, hi and welcome. I suspect you DO need a Weight Distribution Hitch (WDH) and if it can't be installed on your van, the only solution would be to get a different tow vehicle. To prevent sway, a trailer's tongue weight should be between 10-15% of the total trailer's weight. (12'5% is the normal ideal). If it is too light, you can get sway, which can quickly make you go out of control, leading to a catastrophic crash.
The trouble is, 12.5% may put too much load on your van's rear axle, which lifts the front of your van, reducing steering control and greatly reducing your when in a panic stop. A WDH will correct this, and will give you sway control too.
You need to determine your trailer's tongue weight and see if it's enough to prevent sway, but not too much to overload your van's rear axle.
Hi-Lo 1707T - Tire Minder TPMS on Tow Vehicle and Trailer, 300W Solar Battery Charger, Equal-i-zer WDH, Progressive Dynamics Converter, Fan-Tastic Fan
2014 F150 Platinum 4x4 3.5L EcoBoost SCrew