need more information:

1. Any other diseases you have; any medication you are taking, including herbs and supplements.
2. Any recent illness, such as cold, fever, etc.
3. Any changes in your diet/drinking or bowel movements.
4. When do you usually experience your dizziness/lightheadedness, how long does it last, is it related to movement, or position changes.
5. Any other symptoms, such as syncopy, vision changes, headache, palpitation, ect.
6. What tests have you done, and what are the results.
7. How is your menstrual period? Is it still regular? Is it heavy?

Rec: drinking a more water, and rest. Monitor your blood pressure if you can. If any concerning symptoms, go to the ER, or urgent care.
Good luck!