But HOW?

Here is the conversation I had with Carter at 10:55pm- yes, PM last night.
He comes into my room says, "I'm thinking about sad things and feel sad." I bring him back to his room, hold him and rock in his chair and ask why. Here is the conversation while primary church songs play on his CD player.
Carter: Because I'm thinking of Jesus
Me: Those thoughts should be happy thoughts because he loves you so much. Why do you feel sad?
Carter: I don't know.
Me: Sometimes when I feel the spirit and the love that Jesus and Heavenly Father have for me, I feel so happy I cry. Do you think that's what you are feeling?
Carter: Well, I know how the spirit feels, but how can the holy ghost be with me and be with everyone else at the same time?
Me: Because he is a spirit so we can feel him all the time. He lets us know when what we hear is true and when we feel good inside and happy and peaceful, that's the holy ghost also with us.
Carter: Why is he called a ghost?
Me: It's just another name for spirit. We can call him the holy spirit if you want. It just means he doesn't have a body like Heavenly Father and Jesus do.
Carter: Why?
Me: So he can be felt by everyone in the world.
Carter: But how???
Me: I don't understand everything right now, but I have faith and believe that because the spirit does not have a body, we are able to feel him with us.
Carter: Some people didn't believe in Jesus. But I believe in Him. Do you believe in Him mommy?
Me: Yes Carter, I believe in Him. I know he is the son of God.
Carter: Me too. But how cany the holy ghost be with everyone? Can you show me a scripture that talks about that?
Me: (a little stunned, feeling unworthy to be this child's mother b/c I don't have all the answers...not even close). I say, I'll find you one and share it with you in the morning.
Carter: Ok. I think the holy ghost just goes around and around in a big circle (drawing a circle in the air with his finger) super fast so he can get to everyone.
Me: Hmmmm....maybe. But I think he's with us all at the same time.
Carter: But how?
Me: It's like when someone is baptized, they get to become a member of Jesus Christ church and then receive the gift of the holy ghost to be with them all the time when they are doing the things that Heavenly Father wants them to do. If they make a mistake, the holy ghost can't be felt anymore.
Carter: We all make mistakes. Then I'll just pray and make better choices, and then he'll come back.
Me: That's right.
Carter: Good feelings come from God. Bad feelings come from Satan.
Me: (Not sure how deep to go...) Whenever we are making good choices, we feel good and the spirit can be with us. All good things come from God. That's right.
I tuck Carter in tell him I love him and go downstairs to talk to Brady and my brother Matt who just got back from serving a 2 year mission for our church. I tell them the story and ask them for the scripture. I then go back to Carter ready with my D&C 130 28-29 talking about how God and Christ have a body of bones and flesh and the holy ghost is a spirit so he can dwell in us. Feeling satisfied I've given my preschooler some scriptural knowledge and answered his question, he looks at me and says, but HOW?