Pregnant after a hookup

Need some advice. I just found out I’m pregnant after hooking up with someone, we aren’t dating, but we used to talk and be a “thing” and hooked up after a while. My birth control failed, I’m on depo, and never had any problems, but it did. And I’m worried about telling him about the news and how he’s going to react. How should I tell him?

I have a 3 year old already and I’m not worried about having the baby, just worried about his reaction and his involvement as I was in a long term relationship when I was pregnant with my first.