Spinal pressure/pain?

38 weeks today and suddenly experiencing weird spinal pressure and pain that shoots from my lower back all the way up to my head. It is making me a little light headed. I'm only 1 cm dilated (have been for weeks). I haven't heard of this pain/symptom associated with labor (or even pregnancy). Anyone else have this or something similar? I thought maybe it was a migraine at first (though I've never had one) but it's not turning into a headache or anything. Thoughts?