hey there- it could be bowel spasms. Can you get some buscopan. Its a natural product so it won't hurt you if it is not that, but will make a difference if it is! Spasms are so painful and cause the type of pain you are talking about.

also there are glands just above your belly button in your stomach, so it could be them flaring up, esp if you have a virus or getting over one! Esp if your other glands in your neck, underarms or groin are also swallon. That is also painful as well. The only treatment for that is just pain relief.
HTH and you get some relief soon
how about a heat pack???
Odette