Here is a list of safe medicines that my wife's ob doc gave to to us:
fever: tylenol, extra-strength tylenol (max 4000 mg a day)
headache: tylenol, extra-strength tylenol
cough: robitussin, robitussin dm, benedryl
sore throat: chloraseptic spray or lozenges, salt water garrgles
sinus congestion: decongenstant: sudafed (after the first trimester)
nasal spray: ocean spray, afrin nasal spray
antihistamine: benedryl
heartburn: tums, rolaids, mylanta, maalox, pepcid, zantac
constipation: colace, surfak, milk of magnesia, senekot, metamucil, citracel, fibercon
nausea: emetrol
diarreah: imodium ad, kaopectate
this list is what we were told was safe, and we abided by it. You should check with your ob but as far as I can tell, nothing on this list is dangerous.