D.B.
All kids go through phases of feeling rejected or unlovable. Some kids go through phases of just not wanting to be touched that much - sometimes it's a sensory thing (especially in SN kids), sometimes it's the start of independence and feeling more grown up, sometimes they're just ticked off that they can't watch TV).
It's unclear what was said by your ex and his wife. Maybe they said what your 8 year old claims which is awful and inexcusable. But, maybe they didn't. Kids sometimes get confused. Or they extrapolate from a stepparent saying, "I bought this XBox for you because I love you." Then maybe the kid realizes Mom won't buy it, so that means Mom doesn't love him. And sometimes kids who go from home to home just say stuff to get a rise out of one parent.
I think you can't expect kids to understand adult feelings. All you can do is probe more about "What makes you say that? What are some ways that parents show love to kids?" If you continue to have problems, consider some family counseling so that you and your ex can co-parent effectively without competing or selling out the other's values.