Hi. Thanks for your query. Noted your history of boils, large ones oozing pus and were advised Biaxin, Diclofenac, Anvil; started severe vomiting and now have pain, swelling at the tail bone. All this indicate that you have a problem with the small spinal bones at the end called coccyx either due to inflammation as a different entity or have satellite abscess. If so check for diabetes as the first thing. I would advise you to stop the medicines as any one can cause you gastritis, particularly Diclofenac and start over another ones which you must have taken in past and know that did not cause you any problems in the past. Get a clinical evaluation and examination done by a General surgeon. Sitz bath for the tailbone inflammation. If abscesses have formed, please get the incision and drainage, send pus for culture and sensitivity as it will help in future. Take care and you will be fine.