Probably your sciatic nerve, I have both hip pain (mostly at night) and sciatic pain (Sharp pain within hip, worse when I walk). It's just pay of being pregnant, I hope the pain settles for you!
My doctor told me last week that its from the growth of the baby and the pressure they place on (I can't remember the specic name) something in our hip.
Plus baby can lay on nerves
U have extra weight load put upon ur body and swelling tissues and hormones produced that make ur joints relax to prepare for birth I know fun stuff
My physical therapist said it's because when we are prego we use are hip muscles and back lower but muscles the most. Stretch stretch stretch