Thought I was doing great, now feeling terrible, thoughts on my situation?

Hi,
I already created few topics, so you can check them out if you want a deeper explanation. But long story short.
We were together for around a year. He broke up with me in March saying he needs to be alone. Then we got back together after a month or so and things were great. After another 2 months or something, when he was drunk, he told me that he doesn’t feel the same as I.
Then I discovered that he was texting with one girl for like a 3 weeks (even though that we were together) he slept with her the next day he broke up with me and they were together.
I haven’t heard anything about him or them since the break up. Which is already over a two months..

I was really thinking about everything the last few days and I was convinced that I have to move on. That this relationship is not going to happen. That he’s not that person that I thought he was.
I relized that even though I still got him on my mind I’m not thinking about him that often.
I thought that I was on the right path for the last few months.

But then he liked my picture on Instagram. I know that it’s a small thing. But he haven’t do it on the previous ones.
And it started again. Questioning myself why he did it. If he’s still with her. And stuffs like that.
But then I told myself that it was just a reflex. That maybe he even didn’t realized what he was doing or whose photo it is (it was a sunset on a beach from our family vacation).
That was like a week ago. I tried not to think about it. But last night a had a dream about him, well about us. And it really played with my mind, I woke up with tears going on my face.
And when I turned on my phone a saw a messages from him on our group chat, that we have with our mutual friends.
The stupid group chat…
He wrote there something about him and few of our friends going to the Spain and sent some photos of them.
And my eyes started watering and everything felt bad again..
And know I’m constantly thinking about the like. About him. About the girl. If they are still together. How the relationship is going.
I don’t know if it’s his girlfriend or just some random girl. I think it will be weird if he went with his friend to Spain and brought his girlfriend with him. But clearly I don’t know a lot of things about him.
And I don’t want to feel that and act like that..

What do you think? About the like? About the girl? About everything?
I guess that I need someone’s opinion.