hi,
im afraid it sounds pretty bad for your auto box,check that oil level is correct when idling at operating temp and that the oil is not burnt or discoloured, also check what if any fault codes are in the transmission computer (i.e. is the arrow light on the dash?).the position switch and linkage for the gearshift cable should be checked for adjustment as well.
if this lot is ok then you can try to flush the box with new atf oil but if its as bad as you say it probably needs a new or recon box.

steve.