I was misdiagnosed with strep throat and put on penicillin. However some time after, I was instead properly diagnosed with Mono and was advised to stop taking the penicillin. I have been off the penicillin now for a week but have been suffering from severe heart burn/pain in the chest ever since. The pain began at some point while I was taking the penicillin but has only gotten worst since I stopped taking it. What could this be, or what should I do about this excruciating pain?

Report this to your doctor ASAP.