I have two daughters 7yrs and 7mths. No one should ever feel bad for not having kids. Especially if they don't want them.

Your friends are probably just venting (hopefully), so you are hearing the worst of it. Personally, I could never imagine my life without my kids and even though that 7mth old was screaming for a few hours today I wouldn't swap this life for a child free one. It's just different paths and you questioning it probably means you are a good person. Introspection is hard.

My brains a bit fried from the screaming so hopefully this makes sense.