Hello and welcome to PC.
First you need to bear in mind that post partum depression can be different each time and it's very unpredictable as to time and other factors. Second, if you don't feel your med is helping you need to talk to your doc and try something else. You are the best judge as to whether it helps you or not. Don't be afraid to tell doc you want something else.
Above all, DO call 911 or get help asap if you feel like hurting yourself or others.
I've had PPD. PM me if I can help you at all.