Concerned

I had a tubial ligation 8 years ago, my periods we're always on time 28 days in between. I'm scared and unsure what's going on cause as of today October 3,2016 my last period was August 21,2016. I'm 30 years old, my stomach cramps but haven't started yet. I would love to be pregnant again but the chances are very rare. If anyone can help me please give me some info. Thanks