If you have vents in your house, be sure they are clean. If necessary, a professional can come vacuum them out.
Keep the house clean by dusting with a damp rag or static duster, never use a feather duster because it just moves things around. If you must do the cleaning yourself, wear a mask and shower immediately afterward.
Keep the house and especially your bedroom plain and simple. Hard floors are best. Avoid carpeting, heavy drapes, ornaments and clutter, as they attract dust.
The bed itself is a major source of dust. You may want to purchase some dust-proof covers for the bed and pillows. I got some that are very fine fabric, cost about $100. The sheets should be washed in hot water every week, to kill the dust mites.
A daily antihistamine can help a lot, although you might have to try a few different medicines to find one that works well without unpleasant side effects.
As a long term solution, you may want to consider allergy shots. You go get a shot every week for several months, then it drops to once a month. It takes a while to start working, but it can make a big difference in the long run.