Been there, done that.
My first retrieval I was in “twilight” which is the same level of sedation you get for stuff like endoscopies, colonoscopies or intense dental procedures. I wasn’t awake for retrievals two and three, because I didn’t have a good reaction to the sedative.
There was no pain, per se, during the procedure, but there was a lot of discomfort. This is on top of the discomfort brought about by the fertility drugs and the hyperovulation that they caused. (Bloating, abdominal distension, nausea, a sore butt from the nightly injections, tender breasts, PMS-like grouchiness and a tendency to cry at inopportune times that never would’ve warranted tears without the influence of the drugs.) Afterward I felt like I had really intense menstrual cramps for about 24 hours or so. Lots of Tylenol helped.
If you’re going to donate eggs, you need to be aware that you may not have one biological child running around out there who you will never know, you could have several. Multiple eggs are harvested, and because the couple are then going to use IVF, multiple embryos can be created with your eggs, multiple embryos are likely to be implanted and a multiple birth can result. Also, the fertilized eggs can (depending on your contract with the reproductive specialists and/or the couple in question) be frozen and used for a subsequent pregnancy at a later date.