Handicapped but don't look it...what to say?

Don't go through more pain just because people are ignorant. Your placard proves you are disabled. I work with people who have disabilities on a daily basis and a disability isn't always noticeable. The next time you get a rude comment, just tell them that you hope that they aren't in as much pain as you and that they are lucky, that'll make them stop and think before they open their mouth next time. By all means, don't stress about it, stress causes more pain! I have chronic unexplained pain and my heart goes out to you!