First, your doctor chose not to safely taper you off the Celexa completely to see
how you would do off of it, meaning whether you were going to suffer a bad
withdrawal or not, before trying something else. Psychiatrists differ about this, so there's no one way, but my own research shows that the safest way to do this is to complete your withdrawal off of a drug before starting another so you know which effects are withdrawal and which are start-up side effects of the new drug.