Rebound relationship help

I'm having a hard time with the relationship. I was in a relationship in October with a man I've known for several years. It was right after he filed for divorce. We dated for a few months and we broke it off because it got too intense and he said he wasn't ready to commit or be in a serious relationship and that we should just be friends until he was ready to date. I still missed him but it was worth it if it meant him healing and having a healthy relationship with him. Two weeks later you started dating a mutual friend, Stephanie, and they've been out to dinner's going out everywhere together going to events. And right now they are on a vacation together. He still in the middle of a divorce and I'm really lost and confused. I thought I was going to wait for him, we had a really deep connection we've been friends for over seven years. I'm wondering if this is just a rebound relationship with Stephanie. I've heard so much advice from my friends telling me just get over him and he scum, but they don't know him like I know him and I really want to be with him. I want to know if this is just a rebound relationship with Stephanie. Seems like it's going way too fast for to be serious