Given how far along you are, a call to your hospital's advice line is in order. It could be a contraction (since they don't go away with change of activity, position or food), and worth noting if you were dilated at all at your last appointment. Either way, try to eat a snack with protien and carbs in it, if this is the beginning of labor you'll want as much energy in your system as possible since they won't let you eat once you're in the hospital until after the baby is born.
Another possibility is that since your baby is running out of room, he or she has rolled into a position that is comfy for him/her but not so much for you. If that's the case, you can try to gently get the baby to move over by firmly massaging the other side of your body.
at 1:38 AM on Apr. 30, 2009