sharp abdominal pain

For the past 2 years I have been experiencing sharp stomach pains.  I started having these very brief encounters after I done a colon cleanse program that lasted for a few months.  It first would usually wake me up in the middle of the night and sometimes I would break out in a sweat with it hurting so bad.  It would happen on average 2-3 times a month and sometimes would leave me as quick as the feeling coming on but recently have been lasting longer and generally is on the left side of my stomach.  This past week I had pain pretty consistent for 3 days but now I feel fine.  I have paid attention to my diet but haven't found 1 certain thing that I think is triggering my episodes.  I have nausea most all days and feel like I can throw up but only have 1 time, recently.  I have also noticed on days I have my episodes my lower back hurts.  My gen MD thought I had kidney stones and checked me but everything came back fine.  My OB thought I had ovarian cysts but everything came back fine.  Any ideas?