Help!

Amanda • Pregnant with our first - due August 2015!
For about 8 hours now, I've had cramps off and on in my lower stomach and back and lots of Braxton hicks. In the last few hours, I started tracking them and they are about every 3-5 minutes apart. They don't hurt, just tightening, but it seems like an awful lot. Is this normal or should I be concerned? I'm 34 weeks tomorrow.