I don't know anything about Celexa, as I've never been on it. But, I am on Prozac, another SSRI. There was a time when I was on too high a dose and I kept going back and forth from being tired to not sleeping for two weeks straight, it sucked. Then my doctor dropped me down 10 mgs and I was fine. I'm sensitive to side effects. Maybe that's the case with you. You don't mention the dose you're on, but is a lower dose an option? Like instead of 20 mg, try 10 mg? Of course, consult your doctor about it first, though.