Older DH

I am 23 and my husband will soon be 45. We are expecting, I am 7 weeks today. He wanted another child from the beginning (he has two daughters, 14 and 16 from his previous marriage) and he wanted another chance to have a boy to carry his last name. This will be my first child. I'm having a bit of an issue with him because I feel like since this is my first pregnancy he should be as excited as I am. However I feel that because he already had two children he isn't showing much interest in my pregnancy or even acting excited at all. He says he's very happy and he has told his entire family and circle of friends, I just feel like my experience is being robbed from me just because he's already had the experience. I feel like I'm being selfish in a way but then again I feel like he should understand that I am young and want to share this beautiful thing with him and it's like he thinks it's no big deal. After a previous miscarriage tho, it is a HUGE deal to me. Especially considering I was told I had slim chances of ever having children. How can I get him to see my point of view? He thinks I'm just hormonal...which is partially true...but STILL!! Any ideas?