Chronic tummy pain

My 5 year old daughter since January has had stomach pain that comes and goes, she’s had this 5 times. To the point we’ve ended up at the doctors and then A&E. each time they do a wee sample, they say it has a tiny amount of leukocytes in it. They send it to the lab and it comes back clear having not grown any bacteria. It’s always in the same place, she’s missed so much school because of it and she absolutely loves school. It stops her in her tracks when it’s bad, she’ll stop playing and just sit rolling in pain. Has anybody else experienced this? Has anyone else ever experienced this or any idea what it could be/what I could do to get to the bottom of the causes?.