Healthy Lifestyle

I have been having digestive complaints recently, and my doctor said to keep track of what I am eating to see if I am allergic or have something called irritable bowel syndrome. Can anyone reccomend a way of keeping track? I do not really use my phone so I suppose I could keep a journal or food diary. Is there anything specific I should be trying to eat or avoid?

My wife tells me that I eat too much red meat. I usually have meat for dinner every day, with a sandwich or sausage for lunch. Is she right?

My son drinks 3-5 cups of coffee a day, sometimes with an energy drink as well. He works for a tech company and I think that is relatively common there. I think this is far too much, am I correct? What is a normal amount? He is 20.