When did you know??

When did you know your SO was going to pop the question? My SO and I want to start trying to concieve in December. But he hasn't popped the question of marriage or even engagement. I am not worried about it per say, I love him and I don't need a paper to confirm that. I just expected marriage to come first & then the babies. (Not complaining here) when did you know your SO was going to propose? Or how did it happen first for you? Marriage first or baby first?