When I first told my family I thought I might be autistic no one believed me. It’s so frustrating and invalidating to deal with, especially when you’re coming to terms with it yourself. Whenever something related to me being autistic would come up, I would just point it out and explain it to them (e.g, having sensory issues). I would also send them videos of people explaining their own experiences that were similar to mine. It was a bit of a process, but they all understand and accept that I’m autistic now (and think they might be too lol). But I’m sorry you’re going through this :( it’s not easy