2007 Dodge Ram pulling to right.

Have noticed in the last week or so, approx. 500 miles, that my fairly new truck is pulling to the right. If I dont hold the steering wheel 1/2 to 1 inch to the left of center the truck wants to run off the right side of the road. No one else drives it but me. Havent hit anything with it. Checked all 4 tires air pressure. They were 34-35 psi all around. When I get on brakes, 4 wheel disc, there is a small vibration as I come to a stop but the truck doesnt pull any worse to the right than if im driving down the highway at 70mph. Any help appreciated.