You need to talk to your doctor, it sounds like you haven't tried the RIGHT preventer.
They're not all the same, some I've tried makes litterally no difference, while others work really well.
When my asthma is REALLY playing up I can use my brianyl 20 times a day, but the goal should be using it no more than twice a week.
I've been on the preventer I'm on for ages, but I'm going to the doctors tomorrow to see if there's one more suited to my current needs, because I'm not happy with how many symptoms I'm expiriancing.