2000 Jeep Grand Cherokee Exhaust (so it seems) problems

[rgllyd]

I have a 2000 Grand Cherokee 6 cylinder and have been experiencing some weird problems lately. For the last few months there seemed to be a small exhaust leak, but not even noticeable. Lately it seems to have multiplied tenfold but on occassion it goes back to sounding fine. From my experience and exhaust leak can't regress ...or can it??? Needless to say the loud noise at high rpms is disturbing to me (as a driver) and probably the pedestrians who have to deal with it. Please help!!!
-R