Suggest Treatment For Inflamed Cyst Like Pimples

Hi i have had adult acne for 3 years now and its ruining my life, i have been to a dermatologist and wa sprescribed antibiotics and diferin which didn t help .Have been on tetracycline for 2 months and before that was on clyndamycine,nothing helps . I dont want to go on accutane. what can be done for me if anything? Can i ask my doctor for a skin test to find out what s causing it? I have large inflamed cyst like pimples on my neck ,face, chest,shoulders and now around my navel,all very painful and embarrassing .Please can you help.