The problem is that while I'm driving on the highway and a curve forms on the road, my rear end begins to slide from side to side. It used to not do this but all of a sudden it started sliding basically it feels like my car is going to lose control and just spin .I was wondering if anyone else has ever had this problem and how did they fix it. Any help would be useful.

bald tires, blown shocks, bad alignment, bad sway bars,etc.. it could be a number of things.

1998 dodge avenger 4 cyl AT
Mods are:
Not enough

check the air in your tires, tread on teh tires, make sure your struts are good...Have you done anything to your suspension before you realized this?? Even rims??

If not...i am willing to bet its your tires...or there is a lawn knome pushing your rear end whenever you turn...that shit happened to me...it sucks.

Rear Bushings??
I tend to agree with Buck though. Tires are a big cause of a lot of issues. Poor inflation or wear. Look for scalloping or uneven wear patterns and underinflation. While you are under there, look at your rear suspension components. Any signs of excessive wear or looseness? Fluid leaking ut of your struts? Missing bushings?

So now at 44 what the hell do I do?

That's not a description. Most every fucking part of the suspension can cause those symptoms. Start pulling shit apart and tig at it. If you're not comfortable doing that, bring it to a mechanic. But then, why the fuck would you post for advice?

So...why were you e-brake sliding again?