You should call your doctor and ask what medications or treatments are safe. He or she might have other suggestions that will help.
I know it seems strange, but rubbing Vick’s VapoRub on your feet then putting on some thick socks can help a lot, especially at night. I don’t know how or why it works, but it does.
If you can find some raw honey (check with the doctor to make sure this is OK when you’re pregnant), eating a spoonful before bed can also help calm a cough and soothe your throat. I did this last time I had a bad cold, and besides the yumminess it really did help.
Make sure you are staying hydrated, drink some decaf or herbal tea, and get plenty of rest. Have some chicken soup (homemade if you’re up to it, or the freshest, low-sodium variety you can find at the store).