You should ask ur doctor. I know that any pill can harm the baby.... Don't take if the doctor does not give permission!
It's quite possible that you are not, sick at all. Pregnancy increases all of your body fluids, so extra mucous/phlegm can be a product of that. Just relax and take it easy, I've had a stuffed nose for about 10 weeks now. It's frustrating, but there isn't much I can do about it.
On my safe list: sudafed, benadryl, Robitussin-DM, Claritin, Tylenol.
Pregnancy can lower your immune system. Cold and flu like symptoms are very common. Tylenol, Ricola drops, tea and rest are the best remedies.