13 years old, i hardly have any hobbies, and competitive sport isn't my thing?

Try horse riding, It could appeal to your slightly more adventurous side and isn't competitive at all (Unless you want to take part in competitions which you don't have to.) you ski as well then you'll already have the basis for strong legs which is needed and so you probably won't find it too strenuous either and it isn't really a conventional sport. It also incorporates your love for animals because as you ride you build up a relationship with horses etc :)