I will be driving and pulling up to stop and it feels like im getting rear ended and i think its my rear end

DODGE RAM 1500 2500 3500 TRUCK SERVICE REPAIR MANUAL 1999 2000 2001...

get your car fix right now

This is most likely an alignment issue. When you go to replace your tires, ask them to also do a total alignment and it should get rid of the problem.

check the barings in the rear end and on the axles see if the fluid is all over the brakes

Check your transmission fluid. Dont check it in park ! Check it in neutral! Read the dip stick.

drive shaft u-joints will make clanking sound putting in gear or have bad vibration to it . it can be pion bearing in rear-end it will do what you are saying . but check driveshaft , sometimes you can see if drive shaft has play in it move side to side .

I hate to say it but it sounds like you have a severe problem in the rear end. Here are a couple of things i would do. First pull off your tires and wheels. Of course you need to put the truck on jack stands and block the wheels for safety! Disconnect your rear drive line so you know nothing from front diff or trans could be affecting it. Next spin the brake rotors by hand and inspect them for severe damage. Go forwards and backwards. Also listen in your rear end for grinding or clunking noises and also excessive play front foward to reverse. And last drain your oil and put your finger up inside the housing as far as you can and feel for large pieces that should not be there. This should give you a good idea if it is in your braking sytem your rear end or wether you need to start looking at front diff. or the trans. If all is good on rear end do the same thing for front diff and inspect it as well. Make sure you pull front driveline off!

check the play in the pinion gear bearing on the rear end i think! you will find the yoke ie lose and also the bearing has excessive play and needs ro be changed

Check the "U-Joints" on the drive shaft and or rear wheel/axle bearings.
You MAY need a little help as the wheel(s) needs to be of the ground to check axle bearing. Grasp top and bottom of the tire and wobble it in and out.

May seem to be unrelated but, I had a similar problem with my last truck and it wound up being ball joints. It sounds similar, (especially the rocking forward after stop), might be something to check. If you're talking about a 4WD, it could be your transfer case.