Why is the patient experiencing alternating normal and watery bowel movements?

You've had such a bad time with fever and diarrhea. Both could be the cause of your weakness later. The fever and the diarrhea ached your body thus, making you feel tired. You must hydrate yourself with water and soup. Light and easily digestible meals should be your priority. 

In many cases, the buildup of stool in the colon can lead to lower left abdominal pain caused by constipation. Constipation and left side pain can be prevented by increasing fiber intake, proper hydration, regular exercise. If the pain continues or if it is intense, one should seek help from a medical practitioner to clarify this further.

Tummy wind and bowel blockage can be uncomfortable. This condition can also make people poop less regularly. It might happen because of not eating enough fiber, not drinking enough water, or lack of physical activity. Tell your father to eat high-fiber foods such as fruits, vegetables, and whole grains. Additionally, make sure he drinks plenty of water and stays active. Sometimes, medications can cause constipation, so consult the doctor to see if his medications might be the cause.

You have GERD, where stomach acid goes back into the food pipe and causes discomfort. Symptoms of GERD include heartburn, chest pain, and a sore throat. To reduce the intensity you may use smaller quantities of food. Antacids or proton pump inhibitors also affect stomach acids, so when needed, these medications are advised to be taken. Determining the right course of action may be lengthy and difficult for you. But with your commitment and those new lifestyle changes, you may feel many improvements.