Hi. I Have Been Prescribed Sertraline 50mg A Day Four

Hi. I have been prescribed Sertraline 50mg a day four weeks ago. Since that time I experienced a lot of loose stools, nausea, headache. I have started cutting myself, which I have never done before. On Monday I felt a little dizzy during my exam and I had to leave. I went to see my doctor who then doubled my Sertraline dosage and Propranolol, because she believed I suffered from anxiety. The following day I woke up with horrible dizziness and unsteadiness. Since that day I have experienced at least five times a day of diarrhea episodes. I had the first ever serious panic attack during an exam on that day. I was given oxygen because I was not able to breath. My doctor insists that those side effects are not serious and I should still be taking Sertraline. I am not so sure about that.