Dear user, welcome to healthcare magic.
You had your tubes ligated and the pregnancy
test is negative, so you are not pregnant by any means. If it is the first time you experience this menstrual disturbance, try to forget about it and consider it some minor disturbance. If this is recurrent, you should visit your doctor and have an ultrasound
examination to assess your uterus
Anyway, there is nothing serious to worry about in your story.
Dr. Ahmed Bahaa.