I felt the same thing at 30 and still sometimes feel it now at 36, although to a lesser extent as I've worked on it.

My wife and I have been together 13 years and we found out fairly early that we can't have children. It's taken a lot of internal work to be ok with it, good days and bad. Ironically the same 'not over-thinking it' strategy is the most helpful for my well-being. Just focus on what I can do today.

Seems like kids really are the quickest path to meaning making, it takes a lot of active effort to try to get a sense of fulfillment without them, at least for me.