Dizziness nausea cold chills just finish menstruation

Probably a virus: This is almost certainly a viral infection and has nothing to do with your menstrual cycle. The chills may be due to a fever; don't try to lower it unless it reaches 104 as fever helps us fight infections. Drink fluids like chicken or vegetable broth and herbal teas, rest, and consider taking Vitamin C 1000 mg every few hours. If not better in a few days see a doctor.