Wellbutrin can take 4-6 weeks to see full results. However, if you are seeing an anxiety spike I’d be wary. There’s a huge group of people who develop panic attacks taking Wellbutrin (one of my kids is one of them). It can really spike anxiety in a lot of people. Talk with your doctor about what you’re experiencing.
There’s more information and some user reviews here: https://www.additudemag.com/medication/wellbutrin/
ADDitude Community Moderator, Parenting ADHD Coach, Podcaster & Author, Mom to teen w/ ADHD, LDs, and autism