When did you know..

I'm so in love with my boyfriend of two years. I went through a really horrible abusive manipulative relationship with my son's father. And my SO is nothing like that. So sweet, kind hearted and genuinely a good person. Ive never been so happy or in love before. He is great with my son also. I really want to marry him and start a life and have a baby with him and he says he does too but in time. 
So my question when did you know that your SO was going to purpose? Just for fun ☺️