Suggest Remedy For Child With Severe Pain In Ribs

My three year old complains her ribs hurt, she is thin but healthy and eats a good varied diet. I was thin as a child and the reason was none other than an active sporty lifestyle combined with a high metabolism. I wasn t too concerned about the first few complaints but after approx 6 months of regular complaints with the final one being my daughter unable to sit up in the supermarket trolley and crunching her torso in half to ease the pain. Please could you give me done answers or steer toward someone who could help me, thanks. Rebecca