Sounds like you are having a rough time.
Have you ever been tested for anemia? Has your thyroid ever been checked?Has this ever happened before?Do you have any pain with menstruation? Cramps, etc? Are you back on your birth control pills? Have you had your progesterone levels checked?
If you continue to feel lightheaded and dizzy it is important to see a doctor as you may be anemic. Your iron should be checked, and the bleeding must be stopped soon. There is a good chance that your thyroid may be contributing to your symptoms and should be checked ASAP. You should also be checked for fibroids and possibly endometriosis if there is pain with your periods. There is a possibility that you are bleeding this long after missing one pill as your hormones are trying to adjust. However, in my opinion, further testing should be done as well.
In the meantime, make sure you are staying hydrated. Drink plenty of water and/or electrolyte replacement drinks like Gatorade.
Hopefully this helps.
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Glad I could help. Please let me know if you have questions in the future.