I think you need to work on your communication skills here. I am a little confused as if your husband has cheated on you before or you just don't have proof that he has cheated ever or before this time. If he has cheated, I would end it. Cheating is destructive not only to a marriage, It is also damaging to the moral and ethical upbringing of your children. If he has cheated and you really don't want to end things, you both need the help of a good therapist.
If he says he still loves you and you are unhappy, you need to speak up and tell him what you need from him. Tell him what you think is happening to the relationship and how you feel. Mistrust arises from a lack of understanding.
Are you doing your part in the relationship? Sometimes Pregnant women can end up neglecting their husbands to concentrate on the other children or the unborn one. Does your husband know the pressure you are under? If you miss him, tell him to want to spend more time together. From your words, you seem more lonely than angry here. You need to express that to your husband in a healthy way. Instead of focusing on his distance from you, share your fears of isolation when he disappears. He may be overwhelmed and trying to adjust for a second child in his life. Please let me know if I've missed the mark here.
ANSWER THIS QUESTION