Stabbing lower back pain

I'm 24 + 2 and I've been having sharp lower back pain for about 3 weeks now.  Over the past 2 days it has turned into a sharp stabbing pain in my lower back that is consistent for hours.  I've tried rotating a heating pad and ice pack, biofreeze and a prenatal massage and nothing seems to help. The pain is gradually getting worse and I'm starting to get worried. Has anyone experienced this before or know what it could be?