Children with High Blood Pressure

My son has had a reading of 130/69 and sometimes more for quite some time the gastroenterologist does not seem to think he suffers from pre-hypertension and does not want to referr me to a pediatric cardiologist. He also suffered from 3 yrs of age till 9 yrs of age with vomitting to the degreee he rotted out his baby teeth and suffered rootcanals. It took a huge chunk out of my heart,.yes, we saw specialists and no one would diagnose him. I was told he had a sensitive stomach yet his blood work all came back with low amylase and lypase, enzymes that help digest and absorp your food. Alot of his pain has disapated (thank God) but his hair is so so thin on top and he is so skinny. He often still eats very little, and his blood pressure is again pre-hypertension. The most recent doctor refused me enzymes for him and again stated he gained 5lbs this year and at twelve he reads normal on the growth chart. I don't understand this and I'm at my witts end I feel like I'm causing him anxiety but how do I ignore these issues as a mother. Please if anyone knows or can help as to what other steps I can take write. Thank you.