Miranda, in the swimming thread you mentioned maybe taking a lesson or two. It would be well worth your while to do that in order to get comfortable with exhaling under water--there's just not enough time when you turn your head to exhale AND inhale. Gotta do the exhale part under water. I think a few lessons might be fun for you and would make you feel much more at ease. Re shoulders---I also had shoulder pain when I restarted swimming last year. Rotating AND keeping your elbow high during the recovery part of the stroke should help with that pain.
"My predominant feeling is one of gratitude. I have loved and been loved;I have been given much and I have given something in return...Above all, I have been a sentient being, a thinking animal, on this beautiful planet, and that in itself has been an enormous privilege and an adventure." O. Sacks