1996 Ford Ranger

1996 Ford Ranger, 144,000 miles, stick shift. Out of nowhere, my truck starting making weird noises and I have noticed that is off balance--the driver's side of the truck is much lower than the passenger side. When I go over bumps it makes loud cracking-type sounds, almost as if it sounds like something is rattling around in the bed of my truck. I know my back bumper isn't 100% secure, but it has been like that for a long time and these sounds just started today. It is most noticeable when I go over bumps or am on rough roads. When I go over speed bumps, when the back tires go over the speed bump is when the sound seems the worse, that cracking/creakin type sound, and then it goes away until I go over another sort of rough patch of road/bumps. Also, since the sounds started, it seems to be pulling even harder to the right when I drive, especially when I am on the highway going 70+ mph. The alignment was off before this, but now it is an even more annoying/harder pull to the right.

I am assuming this is some sort of suspension problem? I scheduled an appt. To take it in on Friday, any ideas as to what the problem is/how much it should cost to fix?