Oh my, I think a trip to the CAT scale is in order and some cyphering. Like the above posts there are probably some things you can do to minimize the chucking and such, but the root cause is likely to be overloading of your payload limits, at least.
You can try air bags and a different hitch and they will make a difference, but I would get to a scale and see what the situation on loading is. IMO
2007 Chevy 2500HD Classic LBZ Duramax/Allison (Stock)
2005 Bigfoot 1500C8.2 AWESOME