stopped wellbutrin and missed my period with 2 neg tests

I've been on Budeprion XL 300mg (generic Wellbutrin) for 2-3 yrs & have slowly weaned myself off the last 1-2mo. I feel great but concerned about my monthy cycle which used to be every 4 weeks to the day.  My period came two days earlier than scheduled each of the last three months and this month I am almost a week late with 2 negative pregnancy tests.  I've read other posts where women have missed or late periods when starting to take Wellbutrin and some have had miscarriages (my miscarriage was 6 mo. ago).  Anyone miss a period when stopping wellbutrin?