My sister began to have severe depression after having her son, the onset was immediate but unlike some people, her depression didn't go away as time went on. She's a really kind and good person, and she loves her husband and son dearly. She just has to deal with this constant depression.
She's on Zoloft right now, and it helps her mood but she's still dealing with things like constant fatigue and some anxiety. She tries really hard to be as healthy as she can.
Basically, I just wanted to put that bit in just to underline that you're not alone in your feelings/condition. My sister still battles her depression, but she's still a great person and she tries her best. I'm sure you can overcome this and continue your path to feeling better about life. Sorry that it's hard for you right now, but you did the right thing by looking up help--and by posting on here. :)