Recently I Have Been Feeling Really Short Of Breath And

Recently I have been feeling really short of breath and tight chested. I am a diagnosed asthmatic and I take seretide and it's always worked fine for the past 8 years. Ventolin doesn't work for me and I don't have a reliever puffer but I've never really needed one. I don't know why I'm always feeling short of breath suddenly and I keep yawning and taking really deep breaths to try and get enough air in.