It's ok to have self-doubt Oscar, you're in an exceptional circumstance.
It really bugs me in the horror/survival/adventure genre's that the main character(s) mostly seem to have the emotional fortitude (or in my opinion the emotional detachment) to go through the escapade without really having any moments to reflect on how very disastrous and daunting the situation they're in actually is. They don't stop to think "can they actually face this?" "will they ever make it?" They never see a brand of tea and think "this was neighbour John's favorite brand, I wonder if I’ll ever see him again?", and I feel this is an emotional depth that everyone has and should be expressed in all types story telling.
Oscar starts this story light-hearted and innocent, but like with all terrifying and overwhelming experiences, he wont get to stay that way. This is the first real insight into Oscar's true emotions, and if I were in Oscar's position I don’t think I would be terribly functional, I am terrible for emotionally bullying myself out of doing things, let alone anyone else's outside influence. So, I think he's doing quite well all things considered.