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Bingo...Pretty sure this has been answered, but here goes:
What kind of trailer do you have, and what does it weigh? Without that info you're not going to get much help.
The BEST thing for leveling is a weight distribution hitch, set up to get most of your front axle weight put back onto the front axle, and to get you to about 10-12% of your trailer weight on the hitch itself. Without this, anything else is a bandaid that is hiding the problems.
You can put airbags on your truck, and air them up to make the truck sit level again, BUT it doesn't put weight back on your steer tires and does nothing to help control sway. It literally does nothing but raise the back of the truck, and if you're overloaded simply hides the problem.