Have Asthma, Dust Mite Allergy. Having Persistent Cough, Breathing Problems, Blood Shot Eyes. Suggestions?

Hi, i m 39 years old, i have asthma and take seretide 500 for it. i m a swimming teacher and have felt awfall for the last 10months. i have a house dust mite allergy so also use nasonex everyday and have to have anti allergy bedding and keep dust around the house low. for the last 10 months i have a persestant cough that produces clear phelm. i have started to notice that the day after i have been to work i feel awfall, i strugggle to breathe, my eyes are blood shot and have very dark circles under them, i feel so exhausted i dont feel like i can go in to work the next day. so i have a coule of days off start to feel a little better go back to work and feel the same all over again. is it possible that it is my job or is this just a coincidence.