My boyfriend of 4 yrs broke up with me, A week later he slept with another girl, but she told me he wanted her to move in with her, loved her, he even had sex, But after he realized I was really going to give up on him, he wanted me back right away. Did he really love her, or was she just the rebound?

Neither, she was an easy piece on the side. You got dumped so he could have sex, and not have it be called cheating since you were dumped.