25 weeks and cramping

So this morning at 6am I woke up with a horrible back ache and painful pms like cramps. They went away but my lower back is killing me. I called the doc and she said to drink plenty of water considering its been hot out and if the cramps get worse to call her back. So far they have been fine. I'm sure baby ashton is fine because I feel him moving all around. I was just wondering if anyone else has had experience with this and what the outcome was. I'm a FTM so I worry all the time.