I feel stupid

So my husband and I have been married for 2 years and well he’s very very smart and I don’t feel very smart at all. He has a degree in aerospace engineering, and I only graduated from high school. I got pregnant at 17 and had my daughter at 18 so when I met him I already had 2 kiddos. My ex was very abusive and I feel like the little knowledge I did have is all gone now. I can’t hold intellectual conversations with my husband all I end up saying is “yea” or “that makes sense” I do understand what he’s talking about, but I don’t have much to add. I also feel like he doesn’t try and talk to me about anything like that, because he knows I can’t keep up 😔 I feel so inferior and stupid. All the other women he dated in college were smart, I suppose, and then there’s me. I’m afraid he’s going to get tired of me. He joined the military because its something that he has always wanted and well since he’s away he calls or texts, but it’s always like “how was your day?” “I love you” “I miss you” but we never get into deep conversations, I crave it but I don’t know how I would even respond. He gets so excited when someone challenges him intellectually, I can see it in his eyes and I am just here not doing much. What should I do? I want to challenge him and be what he craves.