Am i over thinking?

I know its TMI but i need answers. A year ago i had a tubal ligation done. I had my first real cycle in early September. My husband and i had sex at the end of period. I am also breastfeeding my 1 year old. But she is weening off. I am 2 days late with me missing my new monthly cycle. I took a pregnancy test and it came back negative. I called my ob and she siad if i dont start in a couple of days call them.back and take another pregnancy test. I am cramping like menstrualcycle should start but nothing. And advice? Am i over thinking? Thanks in advance for the tips!