As your periods are not normal, it is difficult to say if you are overdue or not.
The symptoms of dizzy spells, breast tenderness and headache are very non specific and can be due to many reasons.
The best thing would be to do a home pregnancy
test if you think you may be pregnant. If it is negative it may be worthwhile to make an appointment to see your gynecologist to get some information and help with your irregular periods
. If you desire pregnancy, mention it to your doctor and they will probably investigate that too at the same.
Hope this helps in answering your query.