I don't know wether you are using a method of contraception
or not but generally speaking, if you are in the child bearing age and experience any change in your menstrual pattern, a blood test
is mandatory to rule out pregnancy.
If the test comes negative, you may either wait for another week for spontaneous menstruation
or visit your doctor to prescribe you an injection or pills to induce menstruation.
If the test comes positive, you should start taking Folic acid
supplements, and have an ultrasound
scan to confirm a healthy intrauterine pregnancy and to rule out ectopic pregnancy.
Finally I hope these worde were usefull to you and I wish you best luck.
Dr. Ahmed Bahaa.