Congratulations on your 2nd baby!!
I went through PPD after each of my 4 children was born.
It took me several weeks after the birth of my 1st to accept that what I was going through was more than just baby blues, and that I needed medication. Like you, I didn't want to go through that again, but wanted to avoid taking meds while pregnant, if at all possible. I talked to my OB, and we decided I would start medication a couple of hours after the baby was born.
I had a much better experience emotionally after each of my other babies was born, but I did still experience some depression on and off for a couple of weeks until the medication had some time to build up in my system, I guess.
The circumstances of the 2nd, 3rd, and 4th births contributed to the blues though, I think. The last three all had to be delivered via c-section, so in addition to recovering from childbirth, I was recovering from surgery as well. I'm not good post-op even when I DON'T have a newborn- I guess I'm a pretty big baby myself ;)
When my 3rd son was born, we were in the process of getting a brand new modular- which STILL wasn't ready when he was born (bad weather prevented the gas line from being installed- we kept getting snow and freezing temps- even though it was the middle of March). So, my DH and I moved with our 5 yr. old, 20 month old, and newborn 2 hours away from our new home to live w/ my parents and my brother- for 6 weeks :/
It was really nice having my Mom there to help w/ the kids, but my 20 month old got really close to her in the time I was in the hospital. When I came home from the hospital, he didn't want me- just my mom- constantly. I was completely crushed!! In my hormonal mind, I felt I'd lost him.
When my 4th was born, it was the middle of the winter (Feb. 19th), and I have a really hard time with the winter EVERY year starting early Jan. (which is when I start pressuring my DH to move south- he'll wear down eventually....I hope) So feeling trapped indoors really didn't do anything to lift my spirits.
Plus, I had to be readmitted to the hospital w/ an infection the day after I came home from the hospital. When I came home from the hospital the 2nd time, a really bad stomach bug started going through the house. I took care of the newborn while my DH took care of the rest of the kids. Each time 1 would recover, the next child would get it, so my husband spent around 4 days feeding the well kids, while cleaning up after the sick one. He did the laundry, the dishes- pretty much everything. Luckily, he's a nurse and is a very good multi-tasker :)
I don't know how bad your PPD was after your 1st baby- or what sorts of challenges you'll face after this one is born. Your 1st will be 5- so that's good. You won't be dealing w/ potty training or temper tantrums in addition to taking care of your newborn. But really you have to decide what you can handle. You're the only one who knows if you can wait until after the baby is born, or if you need to start sooner.
Very best wishes !!!! :o)