With my second and third child I have experienced PPD. I was on Prozac for a year with my second-born and now I've been on Zoloft for about 3 months or so. I'm still trying (with my doctor) to find the correct dose for me, as things aren't back to "normal" yet. I am, however doing much better in my daily life.
The last thing that I wanted to do was take medication, especially considering that I was (and am) nursing. But after I struggled to deal with the depression on my own for several months after my second child was born, it became obvious that I couldn't do it alone. I had reached a point where I just could not function normally. I would sleep all day and I was always sad, I'd put my oldest in her room and leave my (then) youngest in her playpen and I wouldn't respond to any but their basic needs.
I know better now. After seeing the dramatic change that the medication did, I was much more accepting of it when I realized I was beginning to have the same problems as before once again.
If you wait too long, it will get worse. I'm not saying at all that you absolutely need medication, but I am saying that it's not a terrible thing. They can even find something that is safe for both you and your baby (if you are nursing).
Good luck! If you need someone to talk to, let me know. (I also find that keeping a journal helps me out a lot)