Severe pain after crown prep. taking 5day prednisone, but declined antibios due to history of c diff. am i safe or will pred make dental prob worse?

Antibiotics: Antibiotics are not painkillers. If you need antibiotics it means you have an infection and the tooth needs root canal therapy. Prednisone will not solve your problem. Not treating a tooth that requires root canal therapy will make the problem worse.

Have tooth evaluated: the pain you describe may be linked to an involvement of your nerve inside the tooth. See an endodontist to determine if a root canal is necessary. You need to treat the cause of your pain not just the symptoms

Irritated Pulpitis: also called irreversible pulpitis. The only treatment to save the tooth and alleviate the pain is a root canal therapy. See your dentist for consultation.