I get constant tickles in the back of my throat, then start coughing violently and eventually i start to vomit.

Post nasal drip.: The most common reason for having a throat tickle is allergy. You may or may not have runny/itchy eyes & nose with sneezing . Try non-sedating claritin, (loratadine) zyrtec, or allegra, they should do the trick. This may be a seasonal thing, or may be year round. If it is more of a constant thing, then switch your daily antihistamine every 2-3 months to maintain the effect.

See a doctor: Vomiting after a coughing fit is called post-tussive emesis. It can be caused by chronic sinus problems or chronic allergies but can also be caused by pertussis. You should see a primary care doctor to help sort it out.