My situation might be a little different as I was a victim of a severe adverse reaction to Lexapro last December.
May I ask, how long were you taking Lexapro before the adverse reaction began? What was nature of the adverse reaction (what symptoms did you experience)? How long did this adverse reaction last for? Did you immediately stop taking the Lexapro when the adverse reaction first appeared? Did your ME/CFS-like symptoms appear immediately after the adverse reaction, or some time later?
Are you able to do physical exercise without any difficulty or payback? Usually in ME/CFS, physical exertion leads to post-exertional malaise (PEM), and the PEM can last for several days or even weeks.
Have you found anyone else online who developed an ME/CFS-like syndrome after taking an SSRI drug?
Is it possible that you might have caught a viral infection at around the time when the adverse reaction symptoms appeared, and could it be that your symptoms were actually the result of a virus? ME/CFS typically begins after catching a virus. Around the time of the adverse reaction, did you have any tell-tale signs of a viral infection, such as a sore throat or respiratory infection, gastrointestinal upset, stomach pain, diarrhea, fever and high temperature, etc?
That's not to deny the idea that Lexapro did cause your condition; but just checking that it was not something else, like a virus. Exposure to lots of mold in water-damaged buildings is another reported trigger of ME/CFS.