Boyfriend gets soft

Hey ladies!!! Have any of you experienced your boyfriend doing soft during sex. Everything if great leading up to it, and he’s giving it to you good then out of no where he goes soft? It happened twice to my boyfriend and he’s really sad and upset as to why he doesn’t even understand himself why it happens. I even accused him of not liking me at a point, but I do see that he’s super concerned and questioning is he should see a Dr. Has anyone else experienced this??????