The respiratory system is the system of organs involved in breathing.
There are lots of different types of respiratory problems. Some of them are diseases and some of them exist because of having another illness.
Your G.P. (doctor) is normally the best person to see and talk to so that you can get the right help.
You can find a local G.P. here:
http://www.nhs.uk/servicedirectories/pages/servicesearch.aspx?ServiceType=GP