It's been years, and I still have Feelings for him.

Over the years, I thought about my first ex of 5 years. And it has been, well, 5 years that's passed. And I have been in other relationships but it's just something inside me can't seem to shake him off. I don't know what to do. And I don't want to interrupt his life either, I think it would be a bad idea. Part of me feels like he doesn't even think about me nor feel anything for me. So, I'm kinda alone with my thoughts here. Does anyone have any advice on what to do?