First, stop going to a pediatric dr. you need to find an internist, and more importantly a GI specialist. Your dr just prescribing different laxitives is flat out incompetence.
If you want to go to the ER (which isn't entirely a bad idea) you just walk in. There is no 'getting in' its an ER, just go and tell them whats wrong and you'll see a dr.
What most people dont realize is that the digestive system is made up of a lot of good and bad bacteria. The good bacteria keeps the bad in check and keeps you balanced (regular bowel movements). Due to our ****** diets these days, we don't consume the right foods and therefore our flora (good bacteria) isnt high enough and therefore allows the bad stuff to run wild and cause constipation, bloating, distention, etc.
So first, find a good General Practioner, then find a GI specialist. Sometimes it can take a while to get in to see one, but tell them how bad your situation is and if they cant schedule you soon, go to the ER. They should at least be able to give you something to flush your system out, or at least tell you what to do.
I would also keep drinking water, and a lot of it. Get a very strong probiotic. So go to a health food store or vitamin shop, tell them whats going on and that you need a strong probiotic. You want the ones that are kept cold, with 7 or more strains of good bacteria and at least 50 billion live cultures.
Next, change your diet. No greasy food, no processed food, no dairy, and no gluten. These are all foods that are hard to digest, and you want to make things as easy as possible for your gut.
Get things like chicken and fish, but make sure they are non-gmo and have no antibiotics in them. Get a good, organic coconut oil to cook them in. Also, get organic veggies like spinach, broccoli, carrots, etc. Basically any veggies you like and steam them. Find a dairy free butter to give it flavor (I suggest earth balance).
I'd also suggest going on amazon and buying Digest Gold digestive enzymes, these work wonders and will really help your body break down foods, which should make it easy to pass stools.
I know its a lot to do, but if you do this it should help. Good luck!