Painful spotty bottom

Patient: I suffered from acne rosacea on my face for about 10 years. I’ve been taking Oxytetracycline which keeps it under control. the problem is in the last couple of years I have started to get a spotty bum which has in the past month got considerably worse and very painful.Before the spots were small and red. They some days cover my whole bum and are big angry red and yellow ones which are very painful.