2000 grand cherokee v8 struggles to start and stalls when slowing

Sometimes it wont start on its own and i have to give it gas to get it to start. then have to hold the brake and give gas at same time when i go to shift into drive or reverse. when i slow down to a stop light or sign i have to ride the brake while giving gas to keep from stalling out. when driving a steady speed and not slowing down it is fine. only when starting or under breaking at low speed will it stall out. as long as im above 20 or so miles an hour i can brake just fine with out it wanting to stall out. it does not do this all the time. sometimes it wont want to start, but once i get going it will be fine and not stall at all. other times it will start fine and drive fine for a while then just start acting up for no reason. then some times it drives fine with no troubles at all. the problem has progressively become worse. it used to only happen once every couple weeks or once a month. now it happens about half the time i drive it. and is getting harder to start. it will want to die while idling at a stop light as well, causing me to keep my left foot on break and right on gas to keep the rpms above 1000. i do the same thing when braking. i have to slow down with left foot and keep gas on with right foot. I hope i gave good enough information, any suggestions would be much appreciated. thanks in advance. chris