It is severe the pain, and most likely the worst pain you will ever feel physically, but I wouldn't say it's unbarable, as naturally as long as you start your Labour in a calm mind set you can deal with the pain in your own way, you understand that after a contraction in a few minutes there will be another and it is tiring and still scary evan with a calm mind set as the contractions just keep coming and coming and intensifying, you think there's no way the pain can get worse but it does but you manage it because you have to. I can't imagine how distressing it must be for someone to go into Labour truely scared and panicky that is going to make your labour a lot worse in regards with dealing with pain. Prepare yourself as much as you can, understand that the pain isn't to be scared of and it is very natural be calm and your Labour pain won't feel as unbearable as someone who is in the opposite mind set.