How likely is it for someone to be fined for not showing up for jury duty?

The last time I went, there were several who didn't even show up.

Also, I suffer from anxiety attacks. Shouldn't I be able to be excused permanently due to that, and having ADD? There is no way I can concentrate in that environment.

Yes you can get fine and in some states be jailed for not showing. You may want to try to get a doctor's note regarding your health issues. Have you browsed through the information in LawInfo's Free Legal Resource Center to learn more about your issue yet? See: http://www.lawinfo.com/consumer.html and http://resources.lawinfo.com/en/index.html. You can certainly try to speak to a lawyer to determine what legal options may be available. In the meantime, you may be able to learn more on your own. Search the "Free Legal Resources" tab, or browse the Consumer Resources. Good luck.