With anaemia, that too can make the menstrual cycles to become irregular, either too heavy or scant or complete loss of
periods. If
you have been feeling very
tired, then it is highly likely that
you have anaemia, and in this case you should make an appointment to see your doctor soon and not wait 2-3 months (see my message below with regard to your periods).
Any changes to the menstrual cycle that are not related to pregnancy are not normal.