Just wanted to let you all know that I was suffering from this same feeling pretty much every morning! Was really driving me mad. I had a blood test done on my kidneys and liver and it was all OK. I started to realise that I have been tensing lots throughout the day - holding my stomach in and breathing wrong. (i have had super stressful year but thats a whole other subject!) Anyway, long story short, i went to see a physio and explained the feeling and she said its all to do with my breathing. I'm breathing from my chest instead of abdominally and this puts everything out would you believe. When she explained it, it made much more sense. She gave me 6 stretches/exercises to do morning and night to retrain my breathing but also to relax my lower back. This was less than one week ago and i've done my exercises religiously. I know its early days but i must say the pain has lessened in a morning and i'm relieved to find that it's nothing serious. Not sure if this will help any of you but i wanted to share my experience. Maybe visit your doctor first and get the necessary bloods done to rule out anything serious and then see a physio.