Anxiety/Depression. Not Coping Anymore.

So I'll be talking about this to my doctor tomorrow, but I thought I'd post here and see if any of you other mamas could relate/offer advice. 
I have a 2 year old at home with me (SAHM) and I love her to death. Our bond has always been great. I had PPD with her (I think it was more like post partum anxiety though) and I'm very young. Had her at 20, I'm 22 now and obviously due to have another little girl soon here.
I just kind of wanted to vent here. I went off anti depressants right before I found out I was pregnant again (I've been off and on them since I was 17) and am not willing at all to take meds while I'm pregnant. 
My issue is that I'm just not coping anymore. My mood is plummeting, I can hardly find the motivation to brush my teeth or do the dishes. My stress/anxiety levels have been so high lately. 
I'm constantly stressed about how the baby's doing, my thoughts are always racing, I'm having nightmares and waking up in the middle of the night thinking there's an intruder in the house. I can't bring myself to go far from home because I'm so scared something's going to happen, or I'm going to go into labor. I had my first in 3 hours and am really nervous about how quickly this one's going to come. 
I'm miserable. Nauseous, so exhausted, irritable beyond belief. Crying at the drop of a hat. 
As done as I am being pregnant (stressed about rising BP, was induced with 1st for it, baby's measuring big) I'm also terrified for her to be here and to possibly experience PPD again. 
I don't know how I'm going to do it all with a toddler and a newborn and still feel like myself/make time for myself. 
I'm scared the baby and I won't have a good bond. I look at pictures of my first as a newborn and fall in love all over, but watch YouTube videos of births and newborn homecomings and it terrifies me. As I watch, I can feel this big black hole opening up, and I just feel this huge sense of overwhelming dread. I don't know how to explain it, and I feel terrible even typing it. 
I've gone back and forth whether I want to even ask if they'll induce for this reason. I hate to think my stress levels are affecting the baby. Ideally, I'd like to go into labor naturally, but I know firsthand how important it also is to take care of ourselves so we can take proper care of our children...