I'm soooooo sorry you are going through this and I am also asking those very same questions. Just before my axbf and I broke up he told me how much he loves me and I posses a piece of his heart and to be kind to it, he is there for me forever, he loves me, I'm his favorite girl, he thinks of me constantly blah blah blah. When I asked him if he was seeing another girl he says, no he's not, that his roommate was crazy and he needs to move out, to stop asking him because his patience will be tested because he already said there is nothing he is hiding, that he is not interested in her, blah blah blah. He was sleeping with her. I also ask him if he drinks when I can clearly see he has and he lies and tells me no.
So in short, we'll never really know what was in there heart when it comes to love for family, friends, lovers, .... I like to think that he meant that he loved me, we were together for 2 years, I hope he did. But alcohol is his first love, his roommate would have kicked him out if he keeps getting drunk. So priority is keep roommate so he can drink. I was soooo heart broken and still am but it's getting better.
You are still young and you have a whole lifetime still ahead of you. I hope you find peace in your heart without getting closure from him because even if you could ask him why nothing he says can be truly trusted when they are in active addiction.
I give you a big hugggggggggggggggg and please read lots of people's thread here it will help you. Hang in there and try to focus on you and your healing.