What to do when someone perfect says they have doubts about you (26f,26m)?

I've been dating this guy for the past 2 months and everything was amazing. He put a lot of effort and was so into me. It felt a little bit like obsessive sometimes but not creepy for me, I just accepted that this is how healthy relationships work. I always trusted him and never felt anything bad in my gut.

But two days ago after a little misunderstanding from my part, he just from nowhere says that he is not sure anymore about us. He said he has been thinking and maybe we are not very compatible and he may lost feelings.

This left me completely shocked since we had the best date ever just one day before. He was so happy and we made so many plans for the future. The way he kissed me and looked me in my eyes were signs of a loving person. And the same for me, I showed a lot of interest. I just can't understand how can someone switch from that to complete coldness from one day to another. He was the most green flag guy I've ever met and I just can't believe I lost something that could have finally worked.

Plus today is my graduation day and even knowing that he decided to just ruin it. I know I should be happy that he was honest but still I'm completely heartbroken and can't stop crying. I genuinely don't know what to do.