I'm Desperate to Solve My Daughter's Pain!!!

Hi all- please help!!!!
My daughter is 11 (will be 12 soon). She has had pain in her abdomin- right below her navel going across the whole bikini area about 2 inches wide for almost 2 months straight. She has missed a total of 2 weeks of school because of the pain. We've been to er 4 times in 3 weeks, pediatrician in between and a pediatrics gi specialist yesterday... They seem to all say the same thing- it may be constipation. We were prescribed 17 grams of glycolax 2 times a day, 2 enemas a day for 3 days- she also takes castor oil and lots of water. I also massage her belly every night with olive oil, just to try to relax her which seems to help sometimes., she takes warm baths or showers, and heating pads. 3 x-rays, one abdominal external sonogram were also done to rule out cysts. (she is not menstruationg yet). The pain is unbarable for her, she literally doubles over in her bedroom and will cry from when the pain starts (usually by 8'ish pm-until she gets exhausted and falls asleep, 2, 3, 4 in the morning, imagine doing this for almost 2 months straight every day!) the last time we were in the er-it was because she said she was extremly naseaus and then her vision was blurry for over 2 hours. She doesnt have much of an appetite- what kid doesnt want chocolate?She's lost 5 pounds in 2 weeks. The smell of food makes her sick. I cant see her in pain like this, she says she wants to die!!!!.... I dont know what else to do for her. (i dont get much sleep either, listening to her cry herself to sleep)... Please help me. Can constipation be this bad? Is there something the doctor.'s may be missing. I'm desperate! She's desperate!... Please help. Any info or response is appreciated!