Pain in abdomen when lying down on stomach

I have beenhaving abdominal pain for almost 3 months now. This pain typically only comes when I am wearing tight pants or a tight belt around my belly. This pain also comes when I am laying on my stomach. It sometimes also wakes me up at night, and once I lay on my back, the pain goes away in minutes. I am not sure but I get this feeling that my lower abdomen also feels hard a bit. Please help.

[J.M. Keyes, MD]

Hi there,
There are a number of things that can cause abdominal pain and tenderness- including any organs in your gastronintestinal system, reproductive organs, etc.  It could be from something as simple as constipation, to as serious as a tumor.  It is impossible to tell without getting a full history and doing a physical exam, so you need to see your physician to have serious causes ruled out.  He/she may be able to diagnose you easily with just a history and physical, or more investigation (eg ultrasound/CT/scope) may be necessary.
Good luck.
JMK MD