There could very well be something in your home causing this. You could have a gas leak in the house or some other thing could be causing this. Do you have AC? If so, remember to change the filter every couple of months to keep the air fresh. Do not use too many air fresheners or any other substance emitting things inside the house. To find out what it is, call any company that fixes gas leaks or electrical problems. If you live near any big smoke emitting buildings, this may be the cause and there is barely anything you can do about that.
would you consider your house a warm dry house? if it feels damp, or has a mould problem, also look at your heating, as gas heaters are consdiered a wet heat, compared to dry heat such as a oil column heater for instance.
if your house is quite cold then it could be asthma. and Id def go get them check out by the doctor.
Goodluck!
wow ill pray for you but maybe go to your local health department and explain to them some times the test the air for free or your local fire dept.