Ooh, you sound grouchy! Pain will most definitely do that to a person, but who are you actually angry with?
Thankfully, I do not have any sort of issues that cause me constant pain. For years my pain gauge was my shattered ankle because it was the worst pain I'd ever known. After that my gauge was childbirth of a 9 1/2 pound baby. That one stuck for quite a long while until I needed a root canal. I have insurance, but the co-pay was still over $700 & we just didn't have it so I let it go for as long as I could possibly stand it which was several months of constant throbbing in-your-face (literally) pain that just wouldn't ebb & I couldn't get away from. Eventually I borrowed the money from my mother after I had ended up with an abscess & it just couldn't be let go any longer.
Leading up to that I was NOT a happy camper, but I still carried on & didn't expect other people to understand my pain. Honestly, some people have a higher pain tolerance (I'm one of them) and some have just never had to experience many physically painful situations, bless them. You said it yourself: pain is not equal for everyone.
So again, I ask: who are you actually angry with & why? You're angry at people from years ago telling you that you should have breastfed? Who cares what other people tell you to do! Are you angry at the Dad this morning? You know you handled it appropriately, but I absolutely do NOT think he was acting as though pain isn't real for you just because he asked you to hold his child (whether it was actually necessary at the time or not)who will, I'm assuming, be in your care for the entire day & therefore you should be able to handle holding him in my opinion.