Did the Physician tell you to specifically take it at night. Typically Wellbutrin is taken in the am as it can interfere with sleep. To me it was a much easier medication to take that putting up with the side effects of the SSRI's and SSNRI's. You probably will have to take it for 6-8 weeks before realizing a significant change if in fact it will work for you. Not typically, in my experience, used to treat anxiety. Am trying Sertraline now at 12.5 mg but the side effects are unpleasant, ....somnolence, GI disturbances....but I'll give it a couple of weeks then see.
Hope you will gain benefit! And feel better!