Does He Know What He Is Doing?

So I ask the question, does He know what He is doing? By He, I mean God. Does He know that He is testing my sanity these days. I'm sitting here stressed and worried, AGAIN, about one of my children. My poor eldest daughter is sick and her signs and symptoms have the doctors baffled so they are sending us to PCMC this morning.
They are taking a guess at testing her for thyroid problems, but they are not sure if that is what is going on due to the fact we have no family history and she has had no problems up to now. They say we'll try this and go from here. This just has an eery sense of d'jeveau for me. The last child who had doctors baffled and was sent to PCMC for tests turned out to have terminal cancer. Not that I'm wishing or expecting that again, it's just hard not to let your mind jump immediately there.
I'm just really getting tired of visiting PCMC for my kids. It's not a great place for us. I know I should be glad that we have a children's hospital so close to us, but I would be happier If my kids could stop having to use it. I now have had half our kids up there and I really want to stop.
Is it too much to ask for God to stop testing us and putting Eric and I through the stress and heartache. I really feel like we've had our share. I just want my kids to be healthy and have a little happiness in their lives. Their lives have already been horribly changed and affected by the death of their brother. So much that my youngest daughter keeps asking is she going to die like her brother. So not a question a 5 year old should have to think and ask. My other kids get scared whenever they are sick thinking something horrible will happen to them. Eric and I just keep reassuring them that they will be fine and live a long, happy life. But how do we continue to think this if we keep getting mysterious sicknesses thrown our way with our kids. It truly is a hard thing to think when life is going good and then bam, another kid is being sent to PCMC because doctors are baffled and what is going on.
I just really do hope that God really does know what He is doing. Good or bad, my sanity is being put through the ringer. I just want my kids to be healthy! Is that too much to ask for, I think not. Well hopefully all will go well this morning and over the next few days. Maybe it will turn out to be something really silly and we can get back to normal life. Keep Alexis in your prayers!