Suggest Remedies For Persistent Sinus Infection

Question : I have had a sinus infection for 6 weeks. A Physician Assistant at my otolaryngologist office prescribed 4 weeks of doxycycline, which didn't clear it up. Now he prescribed Levaquin 750 mg. Per day, I've taken 5 of them out of a ten day course. Symptoms are improved a lot but not quite gone. The problem is that they cultured the infection and it showed staph, resistant to everything except Bactrim, and Clindamycin. Last time I took Bactrim I got a rash. Last time I took Clindamycin I had to have simultaneous Flagyl, as a prior course of Clindamycin by itself resulted in CDiff. I have microscopic colitis and irritable bowel so I'm prone to gastrointestinal issues (diarrhea). The PA suggested we could attempt Clindamycin and Flagyl, or a referral to an infectious disease MD. I'm a bit anxious about prospect of IV antibiotics. I'm a 64 year old male, no other major health problems. Looking for advice about the choice between trying Clindamycin plus Flagyl vs. the infectious disease MD. Thanks.