Am I being anxious?!?

I'm 20 weeks into my first pregnancy. Last night, I started getting period-like cramps that carried over into this morning, along with slight lower back pain. My stomach was also very hard almost more then normal. My lower ribs were slightly sore the whole day yesterday. Should I be worried? Google isn't much help; they say it's normal unless it's persistent and very painful. But I'm used to bad period cramps on my normal cycle and I don’t want to accidentally ignore a problem.