Break up

So officially my bf now ex bf and I just broke up and it was pretty bad but we talk about everything and he told me that his feelings just changed towards me and I don’t get how one day he can be In love with me then a few days he’s just over our whole relationship, how is it that he can move forward so fast I’m still very heartbroken and this just happened like three days ago and he’s already saying that’s he’s pretty much over it, I can’t be over it i loved him so much and I’m still so heartbroken, I don’t get why I wasn’t enough for him, I just don’t get it I’m so confused on how he’s moving on so quickly and I really just need help on how to get over this, he was my first love and it sucks that I’m going through this no one should ever go through this