Shooting pelvic pain?

I've been having dull, bruise like pelvic pain for the past 2 weeks. The pain has been increasing leading up to yesterday and today where it's gone from achy bruise pain to sharp, shooting pain. Only comfortable position is on my ball. I'm 28 weeks measuring 30+ weeks. Could this be the onset of labor? I've also had contractions but they are infrequent and vary in strength.