Breast to Formula....HELP!

So I've been breastfeeding my LO for 8 months now and he has NEVER taken formula before, but as a mother of 3 I am tired and pumping is just not working for me. I need all ideas on how to get him to drink formula. I'm ready to enjoy myself again I'm only 27 and my fiance and I can't go no where alone. He cries if he doesn't see me in the room and I just can't take it anymore. Breastfed moms please help me!!!