Its true that antidepressants often stop MDMA from working but I think more importantly think about this;
This isnt a preach about MDMA, I see nothing wrong with safe use of it, but it has a comedown that can lead to depression into the weeks following use.
So isnt it a little contradictory to be taking MDMA on nights out, then citalopram to combat some sort of depression you are having?
You say you take it on nights out...how often? Think, is it contributing to my depression?
As for "will I need to up my dosage" if you decided to take it, I would say take the amount your normally take, else if the anti-depressents have no effect on its effects, you may get more messy than you planned to.