Just curious if you are weaning on your own or under a doctor's care. I have been on celexa over 7 years at different dosages and the changes usually take about 2 weeks before they start to take effect. I usually change by 10 mg at a time (I was up to 80 mg at my worst) and I stay at that dose for at least a month to see how it affects me (taking into account hormones, AF and various stressors that may happen). I check in with my doc, sometimes just a phone call, each time I raise or lower, in case anything doesn't seem right.
As far as side effects, I have gotten the "brain zaps" when I've lowered too much (they're a momentary ringing/buzzing/electrical sensation, you can google it, but if you've had them you probably know what I mean). I have a lot of anxiety during those first 2 weeks, chamomile tea and tylenol pm helps, also limiting caffiene. Good luck and I hope you feel better!