Hello, You have been operated in your nose 8 weeks ago. You got another infection probably in the nose. You are allergic to penicillin, So Tab erythromycin 400 mg was given. After consuming the tab erythromycin you have developed stomach/chest pain along with palpitation. Have you ever taken erythromycin previously and got reaction like this. Understand that even any anti allergic drug can produce allergic reaction for certain individuals. Similarly any antibiotic can produce reaction like what you have even though it has not produced reactions earlier. Stop Erythromycin. Observe whether the complaints are settled. Try to avoid taking some other antibiotic. Consult your Dr regarding treatment without antibiotic. Meanwhile if your complaints are settled after stopping the drug you can take it for granted the reactions are due to tab erythromyin so that you will be careful before getting a further prescription of erythromycin. If your complaints are not settled consult the Dr to find out the etiology for those complaints and get treatment accordingly. I hope you understand. Best wishes