My first is only 8 months just found out I’m pregnant with second

I just recently found out that I’m pregnant with my second baby, we were being as careful as we could be so we thought, but we are happy. I just feel so overwhelmed cause my first is only 8 months I feel like I won’t pay enough attention to her or that she will get behind in milestones. I also feel like my family is not going to be happy for me at all, which makes this hard it’s hard not to care because it’s your family. It’s just so overwhelming & stressful at times... any advice??