How to know if it's a rebound or she left you for him?

So my ex and I were together 4 years, we were each others first love and first sexual partners. I have posted my full story in other posts but basically she left me once 2 years ago and got into a new relationship less than a month after. 2 months later she came back and asked for forgivness. Saying she made a mistake and that even though this new guy was great, he wasn’t me. Then almost exactly 2 years later she left me again, started dating another guy almost immediately, then after 1 1/2 month of NC I contact her and we start talking, and she says she loves me and wants to try again. 3 weeks later she changes her mind saying no, I can’t do this and breaks up with me. I ask her how she could say she loves me and wants to try again and then break up with me. No answer. 2 weeks later I see her with a new guy holding hands. Not the same from before. It’s been over 3 months and they are in a relationship and going strong. They even went on a vacation together 1 month after we broke up for the last time.

I only contacted 3 times total since the break up with pretty much a month in between each time but getting no reply. The last time her father called and told me to stay away or he would call the police. Like I was some sort of abusive or stalker ex boyfriend.

They seem so happy. She hasn’t tried to reach out once. I’m still blocked on facebook and everywhere else. I’ve heard from friends that know him that he is one of those guys who are super kind guys, but a bit boring. He seems to be the perfect boyfriend to her. I was far from perfect, I admit. But I still took care of her, spoiled her, cared for her. We were just both so stubborn so our arguments would get blown out of proportion. So I feel like even though it is a rebound I’m screwed since he is so much better.

Some people says she cheated behind my back/had planned on leaving me and disattached months before. Some say it’s a rebound. How do I know what it is?

My ex was just like that. She broke up with me. Started dating a friend a week later. Last Thursday we talked n got nack together. Yesterday sunday she broke up again. I dont know what is going on.