Sorry to here this, I am a worrier though not to this scale and I do empathise. It sounds a bit like your brain won't let you stop thinking about it, as thinking about it is (seems like) the only way to control it, like keep your enemy in plain sight type thing. It sounds an exhausting way to live though as you have identified.
I used to worry a lot and truth is none of us know where or when something will happen, it is random unfortunately. We can swing the dice in our favour, but never control everything.
I did end up getting an illness and truth is the brain does something unexpected which is that it puts you in coping mode.
Two things happen. Some sort of instinct kicks in where you just deal with what is in front of you, and you also (rightly or wrongly) are more concerned with how other people are coping, because you just sort of accept that it's somewhat out of your hands once it's happened. Humour sometimes plays a part too.
During the same time I lost a friend to illness and there's no skirting around the fact death sucks. Their 2 year old (now 7) is now thriving. The only thing you can control is having some kind of life insurance cover as a parent. They didn't unfortunately but friends rallied round to crowdfund.
The other thing that happens is the NHS come in with a plan, and whatever happens there is a plan (similar to now, your current plan is coping strategies and GP). They do the heavy lifting on the expert knowledge so you can get on with day to day coping.
If like me you find trusting a plan quite difficult, and struggle with uncertainty, I found it helpful to set small goals, for example (just one example), I set a 4 month aim to complete the NHS couch to 5k which took my mind off waiting. I lived in 4-6 month time periods for about five years like that, until I finally moved forwards with it.
So that was how I coped and became more resilient. I do fleetingly worry about practical things but I'm not overtaken by thoughts on it. Hope it may help in some way.