You should be able to take the tussin as long as it doesn't contain decongenstant medication, you simply want the expectorant kind, and cough drops. I would call your doctors office to confirm anything before you start though cause they will want to know. You could have develeped bronchitis or pneumonia at this point since your immune system is weak during pregnancy, I got walking pneumonia my second trimester just by going for a short walk on a nice day when I was getting over a cold : (. But definately drink lots of orange juice and an extra dose of vitaman c to help beat whatever you have.
you can take robitussin products, thats what my doc told me when i was pregnant
I don't know what you are allowed to take when you are pregnant, pharmaceutical or otherwise... but I'd suggest making sure you eat well, stay hydrated. Maybe run a hot shower for a while then go outside in the cold (like when babies have croup---gives some relief). I've heard oil of oregano or eucalyptus oil, a few drops in boiling water, your head with a towel over it and you inhale, can help with phlegm. If you've had your cold for this long, and it's in your chest, you might have bronchitis/pneumonia. If you get a fever, definitely go to the doctor.