Yes, My Husband Is On Bactrim For Prostatitis, Then, During

Yes, my husband is on Bactrim for Prostatitis, then, during his starting this treatment, he has had the flu. Day 5 now, and, he is still very lethargic(totally out of character for him), and, his neck & back have been hurting and his urine is orange. Is this normal. I think the flu has ran it's course, that's why we are wondering if it's the Antibiotic?