It really depends on just how bad you need the medication. What I mean to say is "just how bad is you depression?"
If your depression is and always has been mild, then I think your odds are good that you could do a slow taper and maybe go with a natural product for depression.
If your depression is moderate to severe then you could always switch Celexa for an SSRI such as Zoloft which people say has a lower occurance for weight gain.
Lets also look at the fact that when you first started taking Celexa, you were much younger. With age come added weight and this could be the culpret rather than the drug.
When I was 23 and taking antidepressants I weighed 150Lbs. Now I am 39 and still taking antidepressants and I weigh 185. I am almost positive this weight gain is from age and not from the drugs.