Zegerid and Back pain?

Havnt posted in a while...I ran out of my current prescription of nexium and have been taking some zegerid samples  while waiting for my ins auth to go through.  Anyhow, Zegerid is absolutely by far the most effective med for my gerd; however, I think it may be causing me some pretty annoying low back pain.  I started taking it on Thurs and when I woke up fri I had a lot of pain in my lower back.  I am in sales and sit in a car a lot as well as walk in high heels daily.  Im wondering if anyone else has had a similar side effect or if it could very possibly be unrelated to the meds.  Thanks for any response.  I appreciate it!