Breast milk supply problems

So long story short I had to have a laproscopic surgery due to an IUD perforating through my uterus. Anywho, my milk supply has dramatically dropped due to not being able to feed for several hours day of surgery, and then having to pump and dump milk to be on the safe side since they gave me so many meds. Then afterwards it's been too painful, when he's squirmy at the breast I just can't handle it. So added all togather my supply has dropped and I don't know how to increase it back up. Baby isn't patient enough to keep nursing past my breast produces. I don't know what to do :/ any advice mamas?