I know several people who have cracked ribs due to coughing, however they weren't pregnant at the time.
I tend to be fragile and broke my 4th rib (in my chest) just getting up off the couch. My son heard the crack all the way on the other end of the couch. I felt like I'd been shot and I couldn't breathe.
Cracked or broken ribs are extremely painful. Fortunately for me, I worked at the hospital so radiologoy just called my extension when they had an opening so I didn't have to wait.
My doctor wrapped me, but I took it off because it only added to the feeling that I couldn't breathe. He gave me some vicodin so I could try to sleep at night. Other than that, the only thing that gave me any relief was a heating pad on my chest.
Definitely call your doctor to let them know you suspect you cracked a rib. They should be able to call you back with further feedback prior to your appointment.
Best wishes.