why won't he message me back!! LONG READ

I found this guy in Instagram I have known since I was little - we left the area we were in so I never saw him again. But we started talking since I found him and it was honestly the best thing ever. Butterflies were in my stomach. But we stopped talking!? He made me so happy.... We last spoke about 2 months ago. It wasn't like a goodbye message - we were talking about my grandparents old dog. And he said he couldn't remember the name. So I told him and said some more stuff it that's it. He hasn't responded. He hasn't seen it. And I'm sure the notification would have come up. So I sent one a couple of weeks ago saying did you get any of those messages? He hasn't seen it. He is active because I see he likes things. I'm quiet upset about this as I feel like he is just the most loveliest, handsome guy ever. I feel like I'm not good enough because I'm 3 years younger. Advice?