Son didn’t take news so great 😬

I had my first ultrasound today and after we got home my husband really wanted to tell our 4 yr old son that he’s going to be a big brother. I wanted to wait a little bit longer until I showed and I can break news to him after reading books etc. but my husband was excited. Well he didn’t react so great 😨. He was first confused then he semi smiled and then he got very upset and said “I don’t want to be a big brother, etc.” “when the baby comes I’m giving him away.” He’s been our only one and he doesn’t want that to change and/or have that responsibility of being a big brother .

Girls it got me super sad.. not bc he reacted that way but bc I wanted to wait and got caught up in the moment and I feel like we sprung it on him! I don’t know what to do. Any suggestions? I know kids change etc but I don’t want him to be affected by this!