I'd move on too. It's not because he is "losing feelings" -he made a choice not to maintain the connection from a distance - he should be honest about that -LD is not for everyone (my husband and I made it work and I always had the desire to connect with him by phone, to make plans to see each other etc and when I committed to him I knew we'd be long distance for awhile and on and off and when I committed I committed to maintaining and growing our connection and relationship.
If I realized it wasn't for me I'd have ended it. No one can control how they feel but they can control the reactions - find someone who is fine with how feelings change, ebb, flow and up for maintaining and growing their connection to you even when it's in an ebb stage because you and the relationship and the future are more than worth it. I'm sorry you're disappointed and please don't try to convince him to stay or chalk it off to "overthinking".