My 1995 chevy astro van shakes every time i break

You either have bad brake pads or the bolts are loose that hold the front steering suspension on.

If you are actually stopped and it's doing it then it is not your brake pads/rotors/etc. The 4.3 in the Astro isn't the smoothest engine at idle, but if it's noticeably worse than usual it may need a tune-up or engine mounts, both common issues.

I just had this problem fixed on my 95 astro it need to have the pad and rotors replaced (the rotors were worn uneven and I didn't have enough left to get them turned). But now I can stop on a dime.