Hunk of Cheese,
I didn't see it mentioned here, but do you have the tires properly inflated for the load that they're carrying? Some places just air up the tires to the max inflation pressure on the tire, but that is often times over-inflated for the specific tire & RV/weight combination. I know on our rig that gave a very poor (hard) ride and made steering a bit squirrelly, especially on rough pavement.
It definitely sounds like you need an alignment, but make sure the tires are aired up properly as well, if you haven't done so already. That's an easy and inexpensive fix, especially if you already have weighed the rig ready for travel.
Safe travels,
~Rick
