I Just Found Out I Am Pregnant (going On 5

I just found out I am pregnant (going on 5 weeks), my OBGYN is not in today. I am experiencing some pretty intense cramps in my lower back. So far I've had period- like cramps every day and they seem to be going down each day (only had about 3 today). But now my back is cramping, feels like muscle to me, kind of in my tailbone. Should I be concerned?