Can't Get Over Him

Okay so I was in a relationship with a guy for around 5 months and I've known him for quite a while so I really cared about him and our relationship wasn't the best but I loved it all either way, I was his first girlfriend I believe, he's always been rather secretive but I look past it. Our relationship ended a couple weeks ago because it apparently wasn't working out, but I don't understand why and he's the kind of person that doesn't really care about anything and it hurts to know that he didn't trust me or that he isn't phased that we broke up. He caused a massive argument between my friends because he "didn't see the point in being on good terms" any more. Like dude, just cos we broke up doesn't mean we have to hate each other. I just really love him and none of my friends understand.