I too have had that problem. Here is the answer: first, and this is SCIENTIFICALLLY PROVEN, take at least 200 mg of gingko biloba (standardized extract!) per day, broken up into several daily doses. This will help you with erections in general, so you won’t be impotent. You will need to wait two or three weeks to start seeing the results, but it works.
Also, you can add to this by taking horny goat weed, maca tribulus terrestris and other libido-enhancing herbs (as well as yohimbine, if you do not have a problem with anxiety.)
Second: if you still have problems, switch from Celexa to Effexor, which has a much lower rate of libido problems. that is what I did, and in combination with the herbs, I have no trouble getting wood, or having orgasms (which is the other problem with SSRI antidepressants).
Dangleman