Sudafed, and all other pill-type decongestants are on the big NO list with both my midwives and the OB's at my hospital.
It's much, much better to take a OTC *nosespray* - such as afrin- for a couple of days to keep your nose open, to prevent a sinus infection and enable yourself to sleep. Three days is really the max, and you can alternate sides that you use it on to try and get another day out of it. Of course, this is along with the saline, heat, steam, tea, hydration, all the other suggestions, etc. I'm a veteran sinus infection/allergy/awful nose person, so I have some experience here. The zincam nasal moisturizer- no zinc in it- spray gel works better to keep you moisturized throughout the night than plain saline, and you can use it as much as you want. It's a little pricey but worth it. I also do nasal lavage when I start getting a sinus infection, but that's gross advanced technique right there
My nose stuffiness/allergies/post nasal drip is so severely bad that I do take percription Rhinochort nosespray, and it is a total lifesaver for me. That's more for severe chronic problems, though, not just for a cold. It's category B for pregancy, bless it's little heart.
Antihistamines really won't help a cold per se, but you can try and see how they work for you. Sometimes they dry you up and don't really help the nose, and make you tired and sleep when you really shouldn't because you can't breathe well. On the other hand, if you're having an *allergic* reaction to the virus you have (I get that, which is why my asthma gets much worse with colds), then it can be useful. -j