Experimentation and patience are the keys. You *can* go to doctors/homeopaths who may or may not be able to pin down exactly what is causing the issues, and they might be able to provide solid guidance. However, at the end of the day, you have to try it out for yourself. I've had many friends and family who were told to get off a particular type of food by a practitioner, but when they tested the advice using this method, that food type was fine. Further testing helped them discover which food type was REALLY causing the issues. In other words, even the advice of professionals need to be tested using this method to verify them.
Here's how to do it:
1) Do not make more than one major change to your diet at a time.
2) Remove one major type of item that you think may be affecting you. This could be caffeine, dairy, gluten, soy, nightshades (potatoes, peppers, tomatoes, etc), sugar, or something else if you notice a particular symptom after eating it.
3) Stay off of it 100% for 3-4 weeks straight (no cheating at all, you'll have to start over if you do!).
4) Keep a journal of how you felt along the way.
5) Introduce the food item back into your diet and eat it regularly for 2 weeks. You may notice a difference right away, or it may be more subtle. Either way, keep track in your journal about how you feel.
6) Assess how you feel with it in your diet vs out of your diet and decide if you want to keep it.
7) Repeat the process for each major type of food you wish to test.
I know a mom who was able to pinpoint several food items that gave her all kinds of physical and emotional issues for herself and her kids by using this method. It's slower but more thorough and reliable than testing with doctors in many cases.