Men in general are often misunderstood by women for one reason....we like to assume they are as deep thinkers as we are and sometimes assume something is wrong when they aren't. As if the moments of long silence means they aren't as close to us.
Don't get me wrong, I have known very very deep thinking men as well as a few emotionally aloof women. But what I've found in men is if they have a good job, a home the can count on, love in their life, food on their table, and especially a baby(ies), their thoughts beyond that can become a bit limited. This is not a bad thing if it's the case. It mean all his thoughts are focused on being content with you and your baby.
If you are unhappy, for whatever reason you are unhappy, it's unfair to keep the marriage as it is, letting it break apart slowly and painfully. That's like pulling extra adhesive and waterproof tape off your skin slowly. Whatever you do, don't betray him...no matter what. If you decide you want another kind of marriage, kindly walk away from the marriage, or give him a chance to learn to accept what you want by presenting it kindly. But never break his heart by straying, not to say you would. But it can be tempting when we want our cake and eat it too. That is the wonderful thing about poly in not dealing with that so much. But it's not for everyone. Make sure this is what you want, tell him, then make necessary changes. It hurts to think about making these changes, but please trust me when I tell you the hurt of resolving things in this manner hurt so much less than waiting and have it fall apart later...especially when your child is old enough to understand the hostilities that might follow.
I wish you luck....but just know that if this is only about you thinking your husband is aloof from you...he is probably telling you the truth. It is just how he is. He don't love you any less. Don't mean he'll accept sharing you if you tell him...but he don't love you any less.
Goodluck to you.