Mr1A
I wouldn't worry yourself too much - I dont suffer with asthma however I do have other medical problems that have been picked up on previous medicals.
Normally - as long as it doesnt affect you now, it won't be a problem. If they detect that something is still not 100% they may just write it into your contract that you are aware of your condition and will get yourself check out on a regular basis to ensure you are fit to fly.
With asthma, I can not see any reason why it would prohibit you from any cabin crew vacancy.
Good luck - I hope you hear back soon! Its horrid having to wait for a result but I'm sure you'll have done fine!!!
Abby