Draco hates being alone. He plays it off as if he prefers it that way — and he does at some points. Like, when he wants to read. But not having any friends around or being alone when everyone else is having fun, rather frightens him. He doesn’t want to be ignored or left behind. He wants to make friends with new people, but his pride won’t let him.
Draco had a crush on Hermione, but he hated himself for it. So he’d constantly tell himself he hated her and that she was nothing compared to any other girl he knew. When he saw her at the Yule Ball, he was almost certain he was in love with her. After awhile, he realized how her and Ron interacted; and knew that no matter what he did he would never be anything to her like Ron was. Again, Ron had taken something he wanted, just like he took the possibility of friendship with Harry. He hated Ron, and he continued to hate Ron the most out of the Golden Trio afterwards.
Draco is extremely jealous of the Golden Trio. He wants friendship like theirs. He is mostly jealous of Hermione and Ron — because he wanted to be Harry’s friend. And being denied first year still hurts him even though it was so long ago.