I would take my child to the pediatrician or find a nutritionist.  I believe most health departments have a nutritionist in the office, or at least they can help you locate one.  All of my children (I have five) have went through this stage at one time or another and I know how difficult it can be.  Most of the time it's something they outgrow but I always take them to be checked just to make sure.  You never know, and when it comes to your children I believe it's better to be super safe than sorry.  I wish you the best of luck.