I get pains like what you've described all the time. The first few times it happened I went in and had x-rays - everything looked clear (no collapses, etc.) so it was attributed to "inflammation in the lining of the lungs," AKA Pleurisy, just as thefrogprincess said. I usually take motrin, but since you can't take anti-inflammitories (and if the pain is really bothering you a lot), I'd suggest vicodin or something along those lines. Note though, that vicodin can sometimes have a cough-supressing effect on some people so it's not always a good choice for us CFers - depends on the person I'm told. Also, if it's really concerning you, you might want to get checked out just for peace of mind. Keep us posted on how you're feeling...