Discomfort in lower left back

I am a 32-year-old female and have been experiencing a tingling discomfort in the area of my lower left back--just at my waist.  It doesn't exactly feel muscular, but more like the kind of pain I would normally feel across my lower back during my menstrual cycle.  I am not having my period, and it is not during the time I should be ovulating.  I've felt this discomfort for quite some time (weeks, months?) at night when I lie on my right side.  It feels like there is something pressing and aggravating an organ or something inside.  If my husband lays his arm across my waist, it's even more uncomfortable.  The past few nights I've felt it continually, no matter what side I lie on, and it's kept me from sleeping well.  Even now, well into the day as I sit at my computer, I can feel it.  It's not exactly painful, but it's so uncomfortable and a nagging agitation.  Could this have something to do with my kidneys or another internal cause?  It has been long since I've had regular bowl movements; could this also be a contributor?  Any help you can offer would be so wonderful!  I don't want to worry, but I also want to be wise.