Take many deep breaths. Then make a list of everything that's causing these feelings. Then make two separate lists. One of the thing(s) you can have control over and one of everything else. Then pick one thing that you can affect and write a list of what you can do. THen pick on thing that you can do and do that.
This will break down these seemingly unmanageable conditions to something you can do and this will help you feel less paniced.
I agree that you need to find counseling. Your doctor can point you in the direction of a support group and therapist. Because it's related to lupus your health insurance should pay for it.
Not knowing your support system I suggest that you leave home for a few days and stay with a warm and supportive friend or family member.
Also do call the suicide prevention hotline or a crisis hotline for support. They can also refer you to others who will be helpful.
Lupus is not a death sentence. It may shorten your life but you can have many years of living left to you. Ask your doctor for literature talking about lupus that you can read and pass around to family.