Are Heart Palpitations, Chest Tightness And Feeling Out Of Breath Due To Postpartum Depression ?

I was 6 weeks postpartum when I started getting heart palpitations. They were accompanied with chest tightness and the feeling of not getting a good breath in. I have had EKGs, echo, stress and docs tell me its nothing severe and that it could be because of anxiety. I have never had any problems before. Could it be hormones? or Postpartum depression? Will it go away?