Loose motions are most commonly known as a problem of diarrhea. Diarrhea can be caused by a number of reasons like a gastrointestinal infection and inflammation, over-eating, spicy food, antibiotic use, autoimmune disease, and a host of other reasons. Since you mentioned that you diarrhea has lasted for a few years, this indicates chronic diarrhea. Chronic diarrhea might indicate that you have a lactose intolerance, fructose intolerance, Celiac disease, or Irritable Bowel Syndrome.
Lactose intolerance makes a person unable to digest the milk sugar lactose. The body requires an enzyme called lactase to do this job but in some individuals, this enzyme is lacking. Lactose will then travel in its current state to the intestines. When some of the stomach bacteria come into contact with this substance, their reactions become very haphazard and in the process of trying to breakdown lactose, create gases like methane and hydrogen. These gases can irritate the intestinal walls and cause diarrhea. If you are lactose intolerant, you will find that diarrhea attacks are most frequent after consuming milk and milk related products. Curing this requires that you stop taking any milk and milk derived products. Fructose intolerance or malabsorption is a condition that occurs in people when consuming too much fruit. Fructose is a fruit sugar and a very limited amount can be consumed at a time. When the undigested part of fruit goes into the colon, water cannot be removed by the colon due to the osmotic imbalance. This then causes diarrhea. Celiac disease is a serious disease and is manifested in much more serious symptoms. The symptoms include shock when you consume gluten-based foods like wheat. Irritable Bowel Syndrome is a general categorization for a sensitive intestinal tract that can be caused by some of the other causes.
Chronic diarrhea Treatment - Curing this condition requires that you identify which food causes the diarrhea. Eliminate the items like milk, fruit, and wheat one at a time from you diet and check for reactions. If your condition is still the same, there is a possibility that you stomach bacteria populations are not correct. To correct this, have some probiotic foods for the next few days and check for results. You might have to extend this to one more week to ensure that the correct intestinal bacteria are in your gut. During this time, it is important to also fast for one day in a week to give your digestive system and your intestine a break and clear itself out completely.