Obsession is not healthy because it normally turns into clinging, which is always disastrous. The harder you cling, the more he pushes you away. You could be dating Channing Tatum and if he got clingy with you, I guarantee it would get creepy and annoying.
He clearly doesn't have the same feelings for you, and it sucks a lot. You need to fill your life with things besides him and get rid of what I call "triggers", things that make you think of him. Focus on school, pick up a new hobby and get really good at it. I don't know, whatever works for you.
You said you don't want to burn bridges, but being friends is constantly re-opening the wound. You probably should stop all contact for quite a while, a month or more, to clear your head. He will probably respect you if you explain all of this to him...
You're 19! Don't stress being single.