Having only one child vs adding another

I know it may sound silly to ask random people on an app for advice on a really big life decision but I need help! So I have a 3 month old son; my pregnancy with him was amazing, birth went perfect, and my son is a pretty “easy” baby so far. I go back in forth everyday, “I think one is fine.” and “I want another one.” I just think should we just stop while we are ahead? While we have one good one? I just get scared that our next one will be a terror. But I grew up with 4 siblings and my boyfriend has 3 siblings, and we couldn’t imagine not having siblings. But I think our limit would be two kids. And another thing I’m worried about is being able to give both kids enough attention. Cause right now I can just give all my attention to my son. I want another one but I am just scared that (in a way) I would regret my decision. I know I would love both but just mourn the loss of no longer being able to give all my attention to just one. And I know he’s only 3 months old but I think about this all the time. My boyfriend said he’d support whatever I wanted to do, but he’s probably tired of me one day saying, “only have one.” Or “I think he should have a sibling.” Every other day lol. If we did have another I would want them around 18 months apart, so that is another factor. I just need some opinions on all of this! People that have been in my shoes and were unsure about having another.