You should have more faith in your body's ability to go through labour. If you're convinced that you can't do it without pain medication before it's even started, then for sure, you'll be miserable. Even if you had bad experiences in the past, it doesn't mean the same things will happen this time around. At the end of the day, you'll do what you want, but just know that there are other options to prepare yourself, like hypnobirthing.