I have severe coughing fits that lead to me vomiting. i saw a doctor 7 days ago and he prescribed doxytet, i finished the course but still sick?

Suspected pertussis: This could be consistent with pertussis or 'whooping cough' which in adults may not have the classic whoop. You should see if your doc can test you for that to confirm the diagnosis. There are other meds to help with coughing - so you might want to get a proper cough suppressant (something with dextromethorphan) or even stronger would be codeine (although that is a narcotic and caution is advised)

Doxytet seems to be: the antibiotic doxycycline. This is a broad spectrum antibiotic that is often effective in the treatment of upper respiratory bacterial infections, BUT...you may have a virus or you may have an infection with a pathogen not covered by doxycycline. Symptomatic treatment of cough includes prescription cough suppressant medications and expectorants. Return for re-eval or seek 2nd opinion. Good luck!