I am 38 weeks pregnant and often get a sharp, stabbing like pain in my backside. Is this normal?

Yeah, it's normal. It's usually a sign the baby is posterior and the hardest part of his or her head is resting on a nerve or on your tail bone causing the pain. It could also be general nerve pain, sciatic nerve pain (this usually travels down the back of your thighs too) or just the position the baby is in putting pressure on the back of your pelvis.