My daughter had diarrhea for almost a month, no blood though. At the time we took her off of dairy and the diarrhea stopped. I am sure this is very stressful. I felt like I was being very pushy with the medical staff when my daughter was undergoing multiple tests (dr didn't think they were necessary, but I demanded them). I just tried to remember that my little daughter couldn't advocate for herself, and as her mom I wanted every possible test etc to find out what was going on, so that it could be fixed. Good luck, and I hope your son starts feeling better soon. Don't be afraid to tell the doctor what you want...you are paying them, so in a way, they are working for you.