39 weeks and severe pain in my ass!

So I woke up this morning at 3:30 to make my toddler (14 months) a bottle to get her back to bed. And o my gosh I could barely put pressure on my left leg! I had shooting pains in my left bum cheek. Hurt to do anything. I wanted to cry. Well further digging told me a few things. 1 either baby has dropped and is almost ready to come our or 2 baby is on my siatic nerve. Now if it's one I'll be happy cause I've been in so much pain lately but if it's 2 I want to cry because it's another version of pain that I don't need with a 5 year old and a 14 month old running around. Have any of you had the same pain? What was the cause?