Late period after Fallopian tube removal

I am 33 years old and had my fifth baby via c section 18 months ago. During surgery I also had my Fallopian tubes removed.
Since 3 months pp I have had a regular 28 day cycle but my period is all of a sudden late. Not sure how late as I don't track it at all.
Has anyone else ever had this and why? I do have a doctors appointment in a few days.
I am not under any stress, I am a healthy weight, I don't exercise excessively (or much at all). I am not unwell.
Is it early menopause???
I have no other symptoms like cramps, headaches etc.
TIA