This pain has piqued my curiosity. I've been to a doctor, so I'm not looking for medical advice, I'm just trying to make what 'House' calls a differential diagnosis. I have a dull ache that I would have thought were my kidneys if the doctor hadn't said it's too low for that. It runs inside from my back to my belly, both sides. I have had lower back pain before, from straining my back. This is a similar ache (for comparison), but not in the same place. This is out in my 'wings'. On a scale of 1 to 10, it's a 1 or 2. So not debilitating. What's strange is that it does not hurt when I am vertical. It is only when I go to bed and lie down. Within about 15 minutes the ache starts, and tends to last until I get up. It's enough to cause me to toss and turn to relieve the ache. It hurts when I breathe in very deeply. If I sniff hard, (which works my diaphragm) I can induce the pain (whether that's by the change of pressure within my abdomen, or the flexion of my back muscles I'm not sure.) The reason it's weird is because there is NO ache during the day, no matter what I do. Usually, muscle ache would be there in the background, just not bothering me. I cannot induce any ache during the day. I have ruled out constipation. It's not a kidney infection. Tests ruled that out. I have not gained any weight. (A distended belly might cause this kind of ache.) Any ideas?