PPD question

Is there a way to know if you need to talk to your doctor about PPD? I have two week old twin girls, ftm. I constantly have a pit in the bottom of my stomach because I feel so depressed and I cry for no reason. I am really tired and planning on returning to work soon, which are two more causes of depression. Also I just moved to a new state anout 4 months ago and I'm so lonely here. Advice?