Hi Carmel,
I also had in ectopic about 3 years ago. I also had the same symptoms on and off again the past few months. (very frustrating and scary).
When I am in doubt, I do a home pregnancy test. If I am still worried I do a blood test. That is a pretty sure way to tell, becuase it will pick up even low levels of HCG.
Like you should know, scans and sonars does not pick on ectopics that often.
I have been to the ER a few times with the same pain and symptoms, and was sent home with IBS diagnosis.
However, never ignore the symptoms as ectopics have a tendency to occur again (about 35% chance) in someone who has had one already. Scary, I know. Rather go and see a doctor!
Take care of yourself and hope it is nothing serious!