Dating

I made my boyfriend cry for the first time? Instagram is ruining my relationship? Am I overreacting?

So I've been dating with this guy for 5 months now. He's 21, I'm 20. He recently invited me to his dad's birthday and introduced me to his parents. It all went amazing and when we got back to his place, I felt for the first time since we've known each other that this thing we have is going to last for a long time. So we were going to sleep and I was scrolling through Instagram. I saw that he had added a photo of him (some photoshoot with his band, only he was on the picture) before the birthday and there were many girls commenting it. One girl just put an emoji: 👍🏽 (thumb) and he answered to her with a kiss emoji (😘). When I saw the kiss emoji which my boyfriend wrote, I immediately was like what the hell? He was lying next to me and he laughed at it and said it's nothing special, said that the girl commenting him studies at the same course in university as him. So, I was feeling really bad about it and didn't talk to him for 15 minutes or so. All this time he was trying to hug me and tell me it's nothing, but I just felt how my eyes got teary. I went to the other room and cried. I have been crying in front of him before thet only one time, which was about totally different thing. So he came to the other room and hugged me again and asked what's wrong, that he didn't really meant anything with this emoji. I told him that I've been so stupid all this time and that I probably imagined more of the relationship than him. He just got silent and I heard him start sobbing, for the first time ever. So basically we were both crying there and I went back to bedroom. I was up for like an hour and he still didn't come back to bed. I went back to the other room and he was just laying there, I asked why he didn't come back to bed and he answered "I don't know". So soon he came back to bed and we didn't say a word to each other... Continues in Update...
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Continues... So, I couldn't sleep because of this argument, and sat on the edge of the bed. He asked what am I thinking about and I told him that maybe we should just end this thing. He didn't answer anything, I just heard how his tears fell on the blanket! I felt so horrible. He told me that he feels like I deserve someone better than him, also that he feels like this won't be the last time he makes me cry. I told him not to say it just to make me feel better. He said he trully means this.
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So I told him that I wouldn't be with him if I thought that I deserve better than him. He started hugging me again and it was sooooo sad to see him like this. I asked him if he wanted to end this and he said no. But then why did he say that I deserve someone better? I just don't understand. I said that I don't want to lose him too and he's the best I've ever had. But after this fight I still feel so bad about making him cry.. :( He is such a sweet person, am I overreacting about this IG thing?
I made my boyfriend cry for the first time? Instagram is ruining my relationship? Am I overreacting?
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