"Outta older heartburn!"

My doctor says it is fine to take pepcid so i have been for like 2 weeks, buti found out it was  a catagory b or something. Now I dont quite understand that, when they say the benefits out weigh the risk, What is the risk! I dont want to risk my baby for anything! So I tried to stop it yesterday and the acid is unbearable I took tums all day and they did nothing , I even woke up with laryngitis this morning from it.So I want to take the pepcid again but i cant help but think i am hurting my baby.Can anyone explain catagory B better to me and is anyone else suffering like me?