Hello dear, Thank you for your question. Digestive disorders are a common adverse effect of antibiotics use. These disorders may include: nausea, vomiting, bloating and typically diarrhoea more than constipation. The symptoms usually resolve after discontinuing the antibiotic. Therefore, in my opinion, your complaints are not related to the use of Bactrim. The alternating pattern of diarrhoea and constipation suggest an irritation of the bowel, which can be caused by many factors, including stress. In these cases, I usually suggest to my patients to drink plenty of water and eat a lot of fiber-rich food, which you are already doing. I would also add avoiding alcohol, cigarettes, coffee, processed and spicy food. You may also benefit from use of probiotics, that help balance the normal flora of the bowel. Ask your pharmacist for different options of probiotics. Foods like natural yoghurt and sauerkraut are a natural source of probiotics. If these problems persists more than a couple of weeks after following the suggested regime, please consult a gastroenterologist. I hope this helped you. Best wishes, Dr.Alma