Welbutrin and Period

I've recently been put on a low dosage of Welbutrin to help with balancing my moods with PMDD. I've only been on it a few weeks, we are TTC, and my period is now 10d late. It's never been this late before without a pregnancy but I've taken w test everyday for the past week with negative results. Feeling very frustrated. Has anybody had a side effect of missed periods or late periods with Welbutrin or is there possibly another cause creating a negative on the test and I might actually be pregnant (fingers crossed)?