Natural remedies for colds/boost my immune system?

Hi all-I am based in New Zealand so its winter over here. I've been sooo sick with 2 nasty viral bugs/colds in a matter of weeks and now I'm starting to get a third. The longest I've gone without anything is 1 week :( Any natural remedies I can take that'll help me beat a nasty bug/boost my immune system? I'm finding it REALLY hard. I know my little boy will be worth it all but it's hard when I'm constantly unwell, off work, feverish, coughing till I throw up and miserable-HELP!