Can taking wellbutrin (bupropion) and Zoloft and smoking cannabis cause serotonin syndrome? I've had a few panic attacks that I am worried may actually be ss

Cannabis & serotonin. Cannabis can increase serotonin levels, and definitely should not be used with ssri's like zoloft (sertraline). In fact if you've been struggling with depression and/or anxiety, using any additional drugs is a really bad idea.
Cannabis? Cannabis can cause anxiety, panic attacks and even paranoia. With the problems you have and the medications you take, maybe it would be best to not use cannabis? I would discuss this with your physician to come up with a plan to best address your concerns.