What could intense pains under my belly button, accompanied by constipation, be? constipation persistent for two or more days....

Many things: Too many things to guess at.... Constipation itself can cause intense pain, altough sometimes it is a symptom of another problem - bowel inflammation for example, which could be from many reasons. Bladder infections, hernias, pregnancy....The list goes on. See your dr who will probably run a few tests and get to the bottom of it quickly (no pun intended)!

Backed up?: Lack of normal bowel habit is always a concern; as I do not know anything else about you; and the pains have been persistent i would advise you to get to your doctor for an evaluation. If you cannot move your bowels at all and the pain is "severe" then i would get over to a local emergency room and get checked out. It is better to be safe than sorry.

Abdominal Pain: This needs to be evaluated by a medical doctor or surgeon. You need to have a history, and physical, and then appropriate tests. Please seek medical attention promptly.

Hernia: An umbilical hernia could result in severe pain located behind the belly button. Straining at stooling can exacerbate pain. See a surgeon.