I Am Freaking Out And Confused, I Had My Tubes

I am freaking out and confused, I had my tubes tied during my last c-section April 2013 have had normal periods since even during breast feeding. I had a strange 2 day period a month ago spotted for the whole month them no period, I am now 17 days late took 3 test within the first week of missed period out of fear. I'm not stressed beyond normal parenting, my diet is consistent, no pain, sore breast, I do have ms but that has never messed with my period.