For me it's two things. Some kind of pain I simply cannot recognize. I know something is wrong but I don't see it as pain until I understand I should feel pain. Other types of pain I feel more normally, it sort of depends.

The other aspect is I have never used emotion to communicate pain. I have never cried for attention as a child, I only cried if it hurt. I know that even in the cases I actually feel severe pain people don't believe me because I forget to cry and whine. Also it's a bit of vicious circle because the times I expressed pain people thought I exaggerated so I learned to tone it down even more.