No, it's not appropriate. Such stories are part of very private and intimate experiences that should be kept between the parties involved. Sharing them goes against the respect for privacy and the general standards of decency in society.
Sharing such stories is not appropriate as it involves very private and often inappropriate sexual content. Such topics should be kept within the boundaries of a consensual and private relationship.
It's not okay at all. In most societies, there are clear norms about appropriate relationships. This kind of situation goes against the trust and respect that should exist in a relationship with a girlfriend, and it can lead to a breakdown of multiple relationships and a lot of emotional pain.