I recently had my ductwork replaced and since my home doesn’t have an attic, the ceilings had to be opened up. However when they closed the drywall back up and painted, it started to become very lumpy / droopy. What are my options for fixing this?
Start out by sanding the seams and lumpy areas to determine if it's just a lousy taping job. If so, rip off the old tape and redo. If the drywall is droopy, you'll have to attach it to the joists with more screws. If the paper is separating from the drywall surface, you'll have to replace the drywall with some new drywall.