Why can't I get better?

For the past about 3 weeks I have been very sick. I have been throwing up, had a fever, stuffy nose, and have had a really bad cough/hack. I have gone to the doctor at first they thought I had bronchitis and they prescribed a anti bacteria and some cough medicine… Then I had a relapse which they thought might be strep… But ended up being what they said was bronchitis again and prescribed penicilin… I am done with that and am still coughing and throwing up. Any advice?