I Have Been On Sertraline Or About 3 Weeks Now

I have been on Sertraline or about 3 weeks now after years on Paroxatine. I feel that the depression is just a LITTLE better I am so anxious, to the point that I don't want to be here. I have diazepam too but nothing is really helping. I start to feel better about 11 p.m. How long will it take, if ever to feel any difference. thank you.