I lowered my Lexapro from 15mg-12.5 mg and lately I have had this constant pressure headache I am nauseous, dizzy, and strangely I feel very fatigue. I have been on 4 different SSRI and none have given me these withdrawal effects. All that would happen is I would get anxiety as a withdrawal symptom. I also currently have diarrhea, but I can’t confirm that’s from Lexapro. 
I am back on 15mg because I don’t want to deal with the withdrawals. Let’s just hope the side effects on 15mg get better.