I was on Lexapro for 3 years; the doctor switched me back to Zoloft three weeks ago. First week he cross tapered; second week 100 mgs, and third week after not feeling better I was raised to 150 mgs. I was on Zoloft about 3 years ago before switching to Zoloft. I have to work, as I have children. I am soooo upset. One minute a start to feel fine and then today after work I started crying. The feeling of tightness in my chest is gone and I feel like eating again. How long will it take to work.