An er dr. diangosis me with costochondritis & prescribed me ibuprofen 600mg 3xday. its been 5 days, i still feel a constant dull ache. should i be seen again?

Yes: You should see a local physician to be re-evaluated. Er should be used for emergency visit only, meaning if you have serious pain, and any serious symptoms that need urgent diagnosis and treatment.

Maybe: If you have been ruled out for heart and lung issues you probably don't need another er visit. I would instead go to someone that specializes in musculoskeletal medicine. Manual manipulation can help or injections into the small rib/breast bone joints can bring relief. In the meantime, i would get a large balance ball and lie on your back on it with your arms out to stretch out your chest.