Is my nasal cavity supposed to be open on chest notes?

I find it very easy to switch from mix to head voice. Because I feel like opening my nasal cavity in the back of my palate. But I can’t switch between chest and mix and I’m wondering if I’m doing chest wrong. When I talk I don’t feel that nasally quality I do with head and mix. And that’s the same way I approach my chest: the way I talk. I can open or close off the little space behind my uvula that goes up into my nose. I feel like I’m doing it correctly. Singing chest and closing it off. Singing mix and head and opening it. Why do I find it so hard to transition into the two? My only thought is…I’m probably not doing it right. My teacher says I’m not really good at singing forward. I think it’s cause my tongue tension…I tend to push it back. But maybe foraward singing means to open this nasal cavity area? Honestly I’m not sure. And I’m hoping for clarification!