How do you know it's time to end a relationship?

So, I was with the kids’ dad for almost 10 years, we split up last July, I’m with someone else, but I honestly think I moved on to quick. I still love my kids’ father, and every weekend he comes to get them and I see him, I still feel a connection with him. I don’t want to hurt my current boyfriend’s feelings, but I think I still want to be with my children’s father…