Stomach pain in 2 year old

So my 2 year old will complain at least 2-4 times a week (almost all day long) that his stomach hurts and I've been to his pediatrician about it already and he thought it was maybe for attention but this happens way to much. We've been out camping and all day today on and off he's been saying his tummy hurts and has had not so solid poop 3 times today. He hasn't really ate anything different and I'm not sure what's going on but I'm tired of his doctor not sending him to a specialist for it. He has a small hernia by his belly button but I don't think it's that. Anyone else's little one have this issue? I'm making another appointment and demand he have an ultrasound or something because I need to know what's going on with him!