afraid of commitment 🙄

I've been with my SO for 2 years now and I can't seem to understand why he's so afraid of commitment. I can't figure out why he is this way. I've been waiting and waiting for a ring or some type of promise for the longest. I don't want to just straight out ask him what the deal is but I don't wanna keep wondering. He wants to move forward and try for another child and I want to be stable and completely sure he's committed to me before another baby is conceived. Any advice????