Irritable Bowel Syndrome? Lactose Intolerant or Celiacs Disease? please help thanks?

I have diarrhea or constipation quite often, I notice I get it especially if I drink milk. After drinking it either I get diarrhea/gas or my stomach just feels funny and sometime hurts but goes away if I make a bowel movement. If I eat anything with a lot of oil, my stomach hurts a lot but it goes away after I make a bowel movement in which its either thin/flat or just loose.

I went to a GI about this and he told me to put more fiber (fiber 1 cereal )/fruits/vegetables and less carbs and fatty foods (rice/bread) in my diet in which I did and things went back to normal. But recently I cut down on the fiber cereal and ate more rice and bagels again and the diarrhea, thin stools, came back.

I'm also prone to getting canker sores usually days after if I burned my mouth by eating something too hot. But these sores come in like once every 2 months or so.

Today I ate a slice of wheat bread , oatmeal, and fruits and I feel fine. No aching or diarrhea.

What could this be?

First let me start with: Diarrhea is when your bowel movement is just like taking a pee, only it is brown. So diarrhea is liquid, not thin stools. What you eat is the problem. You have heard everyone state a 'balanced diet' and for a balanced diet you need portion of meat, three portions of veg tables, then you bread if you are still hungry and then the glass of milk. Fiber can be found in breakfast cereals, which you mix with milk and eat. On top of that you need to drink water. So write out on a piece of paper your meals for the week. Breakfast, cereal with milk. Lunch, bread roll with salad, meat, cheese, tuna, or sandwich. Dinner, you can then have a curry with rice. The following day, you can have chicken soup for lunch and fruit, dinner can be pork chop, potato and cabbage. Now as long as you stick to a balanced diet, which meals you do not eat a bagel everyday, let alone three times a day. You do not eat rice everyday, three times a day, try pasta instead. You do not eat chicken three times a day, everyday. You need to mix and match. The key is mix and match, plenty of fiber to 'bulk' up the stools and plenty of water. Good Luck