Given bactrim (sulfamethoxazole and trimethoprim) for infected sweat gland in arm pit, this ok? worried about possible side effects. and how long does it take to work?

Bacterial sensitivit: You seem to have an infected lymph node. Statistically the most common organism is staph. aureus which is killed by a penicillin class antibiotic. If your swelling is going down quickly great; if not then you have to get a new antibiotic and get the lymph node incised and drained if possible by a breast surgeon or gynecologist.