Hi,I am so sorry you have this to worry about.
I think it isn't inevitable, no. I also think that as treatments develop, catching it will become less of a risk (hopefully). I'm treating the vaccine as 'wouldnt it be great but no point waiting for it'
I think the other thing they seemed to think was a factor was 'viral load' so medical staff were at affected as exposed to such high amounts of virus when treating patients.
I would suggest a few things. Firstly be kind to yourself, your health condition means it is quite natural to be worried. You can improve this but not overnight and not likely by giving yourself a hard time. A longer view of reducing anxiety generally will help. Covid is new but fear of illness/dying is age old.
Secondly, decide what you do and don't have to and want to do. Then release what you're not doing it and make the most of what you are doing. Prioritise the really important things. So school is likely to happen, if you decide to send your children back, you may want to reduce other risks.
Thirdly, break time into smaller chunks. What are you doing the next six weeks? Then review. Things with this virus change. So imo there's no point thinking about Christmas yet, we could be anywhere from current levels to full second spike. You can trust that you will respond sensibly.
Remember - everyone is dealing with this and no one has a clue. The very brave people are no more knowledgeable than anyone else, and underneath plenty of them are bricking themselves too! For some overconfidence is not a sign of no fear, it is just the way they deal with fear.
Good luck. 
* Disclaimer: I also don't have a clue and swing from serene to stressed and back again non-stop!