Am I an asshole for wanting to get back with my ex girlfriend?

After 4 years of dating, we broke up with my ex-girlfriend, but since the breakup was mutual, we stayed close friends. We broke up because our relationship wasn't perfect and she wanted to move out of our country and I wanted to stay, and since we weren't perfect for each other I didn't wanted to be the one who keeps her here.
After the breakup, she suggested that we could try again, but I declined since then she would have stayed for me. I even encouraged her to start dating, and now that she has moved away, she found a guy for herself.
I was certain that I would be able to move on, but now that she has someone the realisation hit, that it is completely over. And I miss her very much, and all I want to do is ask her for an other chance, but I cannot do that because she is happy, and I wouldn't do anything that harms her relationship with her new boyfriend. But all I want is to be with her, but I feel like I realised it too late. And I feel awful because I don't want to put her relationship jeopardy by talking to her. But she is my closest friend and the only one I could talk about it.
Am I an asshole for wanting to get back with my ex girlfriend?
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