I am so sorry that you've felt so bad for so long, Mama, and I hope that you feel better soon.
My oh so very unqualified opinion: In my experience, the therapies available for PPD are identical to those used for depression and anxiety not related to pregnancy. PPD is a billing code that doctors use to help you get help for mental health issues with minimal effect on your insurablity later on. So if they're willing to call it PPD, yup, it's PPD.
This is not to say that PPD doesn't exist, or that pregnancy and birth don't have huge effects on mental health - it does, and they do. But whether or not it's "really" PPD doesn't strike me as a question that necessarily needs an answer. If you need help, I support you getting it. There is no denying that PPD is a label that has helped many people get help.
My DD is a post-miscarriage baby as well, and I definitely had some issues connecting to her. Anti-depressants (zoloft and wellbutrin) and sleep helped me immensely. Zoloft is commonly prescribed to pregnant and breast feeding women, but my psychiatrist wanted me to wean before we tried Wellbutrin. Since then, I have learned that many doctors believe that Wellbutrin is safe for nursing women. It breaks my heart a little to think that I could have felt so much better so much sooner without pressure to stop nursing. If you choose to pursue medication and you are still breast feeding, it's important to have a doctor who is well read and experienced in treating nursing mothers.
In terms of natural approaches: for me, I really, *really* needed to get enough sleep. That meant keeping DS in daycare so I could nap when the baby did, and being really unapologetic about going to bed when she did at night. She woke up a lot - we wound up using some sleep training tactics to improve the amount of rest everyone got. (I think that sleep training little babies is nuts, but 19 months is a different ball game.)
In addition, I joined a gym with childcare. On something of a whim, I started a couch to 5K running program, and participated in a magazine-sponsored fitness challenge. Neither of these things has had much measurable effect (I still can't run five whole kilometers without stopping to walk), but I found the structure and the instruction useful in getting me moving. It was a long wait for the endorphins to kick in, but they eventually did.
Connecting with other moms helped me a lot too. I needed the real-world interaction, and I needed people to point things about DD out to me, because, as weird as this may sound, I was having trouble seeing them myself. To me, it seemed like DD was just this inert, unchanging baby thing and we were going to be on this mama and infant treadmill forever. Outside observers were able to point out growth and change and help me realize that she was responding to me (quite sweetly) all the time, and that fostered our connection to each other, which also helped me feel a lot better.