I've cleaned and tried everything and nothing is helping?

Okay I'm still relatively new to this whole "severe allergy" and asthma thing - I just got diagnosed (dust mites are the worst culprit), but since then I have cleaned everything I've gotten covers for all of my bedding, I've used an allergen spray in my spaces. I've been cleaning and dusting regularly. I have a new antihistamine that my doctor recommended but nothing seems to be working. I still cannot breathe every night I wake up unbelievably congested. Any tips? Is it my tissues? I'm still reacting to my bedding? Something else?