Advice for a new step mom?

Wendy
I've been with my SO for 2 years, he has a 5 year old son. Before I got pregnant I played more of a babysitter/aunt/daddy's friend role. Just trying to get him to like me really which has been! We are good friends but now that I'm pregnant and engaged to his father I feel like there is supposed to be a transition from that? I've found myself telling him to listen to his father more and pick up his toys, eat his food, etc. Simple commands. It feels a little awkward but I think that's just because I'm not sure exactly what my role is anymore with him. Any advice or stories are welcome!