Good morning Mojo it sounds like the op went well.
I would recommend taking the painkillers as you don't want to get into the pain spasms cycle like I did after my op.
I couldn't comment on whether that amount of pain after a relatively easy BM is normal after removal of a sentinel pile. But after LIS the pain from the first BM can hurt although not usually as much as you are describing. My BMs did end up causing pain at level 10 after LIS but that was because I had a flare and was having 6 BMs in an hour.
I would think losing blood is normal though as you will have had two incisions one for your LIS and one for the pile.
If you are worried then make sure you ask at the hospital tomorrow.
It will get better Mojo the first couple of days after an op can be traumatic but your body will heal and the pain will reduce dramatically over the next few days
Big hugs