I have sle lupus and recently started taking50 mg tramadol as needed for pain. now i clenching my jaw and bite tongue at night. is that the cause?

Not likely.: You will not see this listed as a side-effect. It might be possible, but another cause is more liekly!

No: You just found out you have an autoimmune disease. This is a stressful time for you. This stress is manifested by clenching. Visit your dentist and discuss w/ them about a possible night guard. Once you start managing your disease, things will settle down and you will clench less.