3 times in the past two months my son has had a very sudden episode of what he calls "hip" pain. He is 7 so I can't tell exactly if it is in fact his hip or something abdominal. It has always been on his left side straight across from his belly button. It comes suddenly with no warning and he cries out in pain, not wanting to move. When he does move the pain seems to worsen. 2 of the 3 times he has been in bed when it has happened. The episodes last 10-30 minutes and then leave almost as suddenly as they came and then he is fine. He once said that it felt like something was going to pop. I'm wondering if it is a hip socket thing. However, nothing ever does pop he says. He describes what happens as it gets easier to move as something "bubbling up inside". He has no other symptoms with this, no redness, swelling, or discoloration. Any ideas on what this is?