What Causes Delayed Period After Tying Tubes?

My last normal period was followed up 2 weeks later with a heavy period. Now calculating from the unexpected one I should have started yesterday (28 days, but am usually early). I have been experiencing cramps for 2 days, but no blood or spotting (usually have spotting 1-3 days prior. I am 48 years old and had my tubes tied in 2003. I have my annual appointment scheduled for end of June. Am hoping just pre-menapause, but am wondering if this is a usual symptom of this.