Bloating, Nausea, stomach pain. I avoid?

I am a 39 year old female. I have been feeling bloated and nauseous for last one week or so. I have also been having occasional stomach pain or pain in lower abdomen. On Monday there was a little blood with stool. Happened twice on Monday but there has not been any more blood in stool since then. Stools are soft and are passed 2-4 times a day in last 1 week or so. General feeling of fatigue and weakness. Could it be stomach infection? What medicines should I take to recover? I generally have a pretty demanding lifestyle and often skip breakfast and have lunch around 1/1:30 pm. What foods should I eat and what should I avoid? I have long work hours and food intake can be erratic at times. Please advise.