Generally, the only reason to add Wellbutrin to an ssri such as Lexapro is that a very common side effect of ssris is weight gain. Because Wellbutrin is a very stimulating antidepressant, it tends to offset this problem. If you're still having the problem, it's probably the Lexapro and the Wellbutrin probably isn't working to alleviate the problem. My own experience is that there's virtually nothing that helps stop weight gain from antidepressants except stopping them, but if this is working well for you, and you really need meds, it's not easy to find ones that work well. There is a book that discusses this called The AntiDepressant Survival Guide. The diet it suggests isn't very good and it's an old book, but it might give you some ideas of how to at least try and work with this, but again, one of the most effective ways to deal with this is to add Wellbutrin and it obviously isn't working for you.