I'm going to tell you exactly what our preacher told us in church on Sunday. Take a nap. He said that so many moms come to him, exhausted and stressed out, and think they're just the worst mothers on the face of the earth. He tells them that they need to take a nap and become refreshed. Once you've gotten some sleep, the things that are stressing you out, will become more manageable. You said that your kids have been sick, and in my opinion, croup is the worst. You stay up with them all night just to make sure they're breathing. It's the scariest thing my kids have had and my oldest is eleven.
I have three children age 11, 7, and 3. When my 3 year old was 2, I thought I had PPD myself. I'm not sure how late it can show up, but I'd call my OB/GYN to check into it.
You have an awful lot on your plate right now and it sounds like you are just at the end of your rope is all. Regular depression is something else that could have kicked in at this point and is only exacerbated by no sleep. If your OB/GYN doesn't think it's PPD, then talk to your regular doctor. Don't let it get ahead of you. I have so many friends, including myself, that have suffered from depression at one point or time in our lives. Especially after having children. I had to take anti-depressants for 3 months until my chemical imbalance got straightened out and I haven't had to take them since. Sometimes that's all it takes. :o)
As for your husband......you can't make him happy. If all this started after the accident and he hasn't come out of it yet, he needs to go see his doctor or a counselor. If you go to church, he could go speak with your pastor. He needs some help because it sounds like he's depressed as well. That accident may have made him realize how out of control of situations we all are. Just know that he's the only one who can make him happy, not you. Focus on you right now and get you and that baby girl well.
I will pray for your grandpa and your dad. The medical world is so advanced right now, so try not to worry about this until you need to. I know.......easier said than done. :o) I will also pray for you and your children. You have got a lot of responsibility resting on your shoulders right now and I know there are certain things you can't quit doing, but if there is anything in your life that you can put on hold for now, do it. Take a rest. Take a nap. :o)