First, good job on being aware of what's going on - how your feeling, noticing how your daughter's feeling, and taking steps to see the doctor about it!!!
Second, I understand wanting to stay away from medicines like antidepressants, but they may actually do you a world of good right now. You probably won't need to stay on them for very long. Part of the feelings you're having I'm certain are related to PPD. I grew up (wrongfully) thinking that antidepressants weren't something "normal people" needed, and I should just "suck it up" and everything would be fine. I've been through depression, and when PPD hit, that was a whole new ballgame. I went straight to the dr. and said, "I soooo need help!! People say hello to me and I start bawling!" I took Sarafem for about 6 weeks, and it was a huge help. Just keep repeating to yourself, "It is not a sin to take antidepressants!" It would be a bad thing to avoid taking them when it could help you deal with PPD better. You take pain medicine for physical injuries, so why not take antidepressants for the emotional injury?
Next, thank you older daughter for being so sweet. Maybe she could help with "booty duty" - she could help hand you wipes while you're changing the baby, get a drink of water, get something for the baby to wear. She needs to be included in the process - and that'll help the 3 of you bond.
It was hard for me bonding with both my daughters too. The people at the hospital were useless in the breastfeeding area with my first daughter, with my second, they wouldn't leave me alone! I still ended up using a bottle with both. I just had to hold them and say, "You are my sweet girl, and I love you so much..." and it was one of those things of you say it enough and it comes true sorts of things.
Good luck!!! Hope everything goes well with the dr. appointment.