Hi there. I actually had my kiddos back to back. :>) I had a 6 month old when I found out I was pregnant with baby number two. SURPRISE!! LOL It's all good. I will not lie to you though, it was very hard. Times were stressful for about 4 to 5 years when they were babies and toddlers together. But we made it through. Your partner is probably pretty aware that it will be tough. Many couples have a hard time during those years---- there is little time for each other, little money, everyone is sleep deprived, etc. So, he's voiced that it is too soon for him. He's being honest and that he feels this way is valid. Talk to him about what it would look like to keep and raise this baby together. See if you can soften him. :>) But being empathetic about his feelings WILL help.
I'm here if you want to chat about this. It will all work out. hugs