On the breathlessness front, a conversation with your GP could help.
I have lots of physical health problems, which at one point were causing me a lot of stress and I started to worry I couldn't tell what was anxiety and what were signs of my actual physical health deteriorating.
My GP talked me through the difference in sensation and symptoms between anxiety breathlessness and breathlessness caused by heart/chest problems etc. Which I found really helpful and reassuring, because it meant I knew how to respond and when to worry vs when to focus on calming myself down!
We also had helpful conversations on the rest so I feel I can trust my body and what it's telling me now as to whether it's because of my illnesses, or whether it's the stress/anxiety of dealing with them/life in general.
If you could have a conversation like that on the breathless front I think it would probably set your mind at rest - you'd know you could trust your judgment about whether you needed medical help or not if it happened again - and that might start to settle you more. It could all be anxiety, it could all be physical, or it could be that it started with something physical and you've become so worried all the extra stuff is now anxiety symptoms.
It is easier to differentiate between anxiety and physical illness if you can reduce the anxiety caused by some of the symptoms, even though it feels like trying to break a very vicious cycle. If you respond to yourself in a calm, gentle, reassuring way and pay attention to how your body feels as you focus on calm and reassurance it can show you what's going on. E.g. If you feel or listen to your pulse as you focus on reassuring yourself you'll be able to hear it gradually slow back down to a normal rate... then you'll know a) what you're doing is working, and b) it's just panic, and c) you have some control. But you do have to be making conscious efforts to calm yourself at the same time.
I hope you get to the bottom of things.