I mean, to be fair, being a young Slowpoke living around many Slowbro and few - albeit still considerably rare - Slowking, it would be pretty reasonable to wish for evolution at some point, yes? In fact, I’m sure all young Pokémon think this at some point. Clearly you have at some point, as well!
And, if I recall correctly, I believe I mentioned I was asleep during my own evolution… So! I did not feel a thing myself, ahaha…!
Actually, speaking of that, even if I were awake, I probably still wouldn’t have felt any pain - at least not right away. You see, our species tend to react very…slowly…to many things, such as pain; hence our name! Many believe that because we don’t react to pain and such immediately, that we’re too “dumb” or “dense” to realize we’ve been hurt at all. Truthfully, though, we are just slow to the reaction of it is all. Since our pain receptors tend to not react immediately, our species is relatively tolerant to pain, depending on the severity of course.
However, others still tend to be insensitive to our feelings and still refer to us as such. Since we’re “slow” that means to them we’re “dopey,” when that really isn’t the case. It’s actually quite hurtful…