Just wanted to say that a friend's DS had the same thing and had to have blood tests to determine what it was caused from. I'm not sure exactly what the results said but I know for sure that it wasn't anything serious at all.
Just wanted to give you a positive story. Big hugs hun.. My DS had to have a blood test when he was 3 months old and it was the most awful, traumatising experience for both him and me. I have everything crossed the test results come back all clear x