Welcome to you Welshbesam. I'm sorry you've had this fright.
Perhaps it's a good thing this has happened now while you're still young and fit enough to make a difference to your future.
Some of us started off with asthma and it's progressed to something else.
You have the opportunity now to get your lungs in good shape and also your muscles fit, strong and efficient - see other blog on oxygen which has helped me enormously to understand the importance of being fit. This will help to prevent any deterioration of your lungs.
I too had mild asthma diagnosed diagnosed 9 years ago. I now realised I'd had it all my life, badly and untreated as a small child. As an adult I was mostly super fit(!!). It made no impact on my life at all bar walking in hills, mountains & certain exersises for ie the cross trainer.
God, I wish I knew 3 years ago what was coming I might not have sat on my arse & got low & unfit.
No one tells you you have to change your life a bit to avoid ill health in the future. For instance, did you know you must avoid mould spores like the plague? I do now but only from being quite ill and having a few tests.
It feels like your life is over but this site will teach you that isn't so. Ask any questions even if you think they're trivial.
Take good care of yourself, eat healthily, lose weight if you need to, learn breathing exersises to strengthen your lungs, always ask for the results of any tests - the GP practice wont necessarily let you know, be pro-active, get some Manuka honey, avoid people with coughs and sneezes and above all - as others have said - ensure you're taking your preventive properly. I think I probably wasn't so have suffered needlessly.
All the best to you. P