I have been possibly exposed to chickenpox, and have lupus, what should I do now?

Infection. Call your primary care doctor. If you have been exposed in the past and/or vaccinated, you should be safe. The risk is if you are on immunosuppressant therapy for lupus. They might want you to simply watch for symptoms but better to be safe and call.
Talk with Dr. If you had chickenpox as a kid you are likely ok, but your lupus can play games with your immunity. Talk with your doctor about the exposure. There are some medications which can supress the varicella virus if you are susceptable;however, use of any such product should be discussed with the providers who know your case.