5 yr old male, pain around belly button for 3 weeks, sediment test rate 24

[Olliepunkgurl]

My son is 5. Over 3 weeks ago he woke up vomiting terribly, chills, shaking, crying. Since he has complained of pain around his belly button, extending to the right side and recently around the groin area. When asked where he hurts, he points in his mouth, down his throat, and to his belly button. He has not continued vomiting and has had no fever, but continues to have pain in the areas mentioned. His pain is worse in the morning and evening, however in the day he has had advil/ibuprofen.
We believe it could be beginning of appendicitis, his doctor does not. He has had blood tests, lived function tests, sonograms, celiac tests, and a sediment rate test which was 24, which is above normal definitely. The doctor thinks he is "backed up", according to sonogram, and has requested we use miralax to help clear him out. We did, he has cleared out quite a lot, yet is still experiencing pain, even crying and begging for medicine. Some of the lab work came back close to being above normal, such as leukocytes being 11, highest for normal range being 11.5.
Im at a loss as what to do from here. He really says he hurts, and looks like he does when he is upset, crying, etc. I don't like him in pain, and don't want to continue giving him advil. I don't know what to do. Ive been to his doctor 3 times, with no change.
Any ideas on my next step? I do have his test results if that would help. Thanks in advance.
P.s. he is typically a very happy, healthy, energetic boy.....currently he is missing school, not wanting to go to birthdays, and is worried he might not make his own party sunday. :(