Toddler with diarrhea question

I have an 18 month old son who has issues with diarrhea.  At times it will last for weeks as a runny mess before becoming at best soft and mushy.  Other times it will only last a day or two and return to a mushy state.  He has had a blood test for allergies, and nothing came back positive.  He has also been tested for all sorts of infectious agents and again all results were negative.  This has been going on for at least a year.    He does not drink juice.  I try to give hormone and pesticide free food and use natural ingredients as much as possible.  The pediatrician said I need to wait for the diarrhea to continue for atleast 4 week before he will order additional tests.   His growth has been steady as is his appetite (the main reason why the pediatrician has not been concerned).     He is not yet talking and is seen by a speech therapist (his pediatrician thought the two may be connected??).  I have no idea if this is also related, but he still has a hard time with body temperature and staying warm at night, and seems to get more "colds" than any child I have ever known.  Any resources or suggestions would be appreciated,

Thank you

[Renee Radenberg]

It is important your son is growing and he has a good appetite. Has your son been tested for dairy allergies or parasites? You might want to consider going to another MD for a second opinion because of the length of time your son has had diarrhea with possible malabsorption.
Thank you and best of luck.

[musikal101]

I have been considering another MD.  all tests for allergies and parasites have been negative.  thank you.

[Renee Radenberg]

I wish you the best.