Hi...this is just my opinion and experience. I didn't have any unbearbale side effects from Lexapro when I first started taking it. I started taking it about a year and a half ago for anxiety, not my fibro. Then I noticed my fibro started to act up badly as well as my RLS. Then after trying to taper off, I started getting brain zaps. Of course I looked up side effects and there at the top of the list was increased muscle/joint pain, exasberated RLS symptoms and the good ole brain zaps. This is after being on the drug for a year. I have since researched SSRI's and this can happen after years of taking the drug...out of nowhere. I don't know if the diarrhea is caused by the Celexa or not...I'm just saying the side effects can come at any time, no matter how long you have been taking them. SSRI's help many people get through their darkest hour and I'm not suggesting to anyone that they don't take them if they need them. I just think that doctors should start patients on these drugs very slowly with tiny pieces at a time, then warn us about what can happen when we try to go off them. Mine didn't.
I have read the same info as you, the sx can happen with forgetting to take a dose of the drug, with increases in the meds and with weaning off and yes it may be weeks after you stop the med you have sx.
I have been off Cymbalta for 8 weeks now and I have had the anxiety off and on. Some times it is really bad then again it is OK. I am hoping this will go away.
I would like to blame the tuna for your diarrhea problems. But do not know for sure. :) Take care.