Increase fluid intake, use a humidifier, try a saline nasal rinse (I love these), and extra vitamin c. If you have a fever or trouble breathing you need to go to the hospital. Decreased oxygen for you means decreased oxygen for baby. Fever for you means higher body temp which is also dangerous for baby. I'm all for natural remedies but you need to weigh the pros and cons.
I had it two weeks ago in full force...coughing, congestion, nausea...I ended up in the hospital on an IV for a night, which cured the nausea. As far as the coughing and congestion go, I doubled my daily vitamin C (Emergen-C works best for me); and steamed mint leaves (boil them, then sit over the pot with a sheet or something over your head for about 30 minutes). I also made my own vitamin water using mint leaves and lemon and lime slices. I've always preferred natural remedies to medicines, so I've been doing this for years.
I had similar symptoms when I was about 20 weeks pregnant and went to see my doc and I had tonsillitis, 5 days of antibiotics and all fine. It was hard for me cause I hate taking medication but in some cases it does baby more harm to suffer with symptoms (if it's a infection and not just a common cold). I would go see your doc and see, you may have a virus that you can get rid of yourself but it's always better to be safe than sorry.
Call your doctor immediately. If you have the flu, this can pose serious risks to you and baby.