Daria, I am on the same dose of Lexapro, and my motivation got very very low, too. My doctor added another medication on top of it, bupropion, which is more stimulating. For whatever reason, that combination has worked for me for a couple of years now. (Until the present moment, when alcohol-less-ness has thrown me into a bit of a funk, hopefully temporary.)
Obviously I can't give medical advice, but I think it's safe to say if your medication is making you feel worse, you need to fix that.
xoxox