Occasionally when I think about eating I get nauseous

My boyfriend says that's not normal and was getting mad at me for not going to the doctor. It's not pregnancy because it's happened multiple times, just not frequently. What happens is even if I am hungry, thinking about food or eating food makes me nauseous. Like today, I was Really hungry, made food and could barely eat it. This will go on for days and I won't eat or I'll barely eat. One time I lost 10 pounds. I'm only 115 lbs as it is. What's wrong? I've been to the doctor for too many things.