Disconnect with long distance relationship?

I am in a long distance relationship where we see each other once a month and we plan on moving in together in a couple months. When he's here everything is fine, when we're apart we argue almost daily recently. I dread the moment he has to leave because what we have in person becomes nonexistent when we're apart. Normally unresolved issues get swept under the carpet when he gets here as to not waste the time that he is here and because he normally makes like they don't exist, when he leaves it all hits me like a truck again and I can't bring it up because I either come of as bipolar or he withdraws and either pretends all his fine and expects me to do the same or he goes silent until I get upset and end the conversation. It's like he's two different people in person and over the phone. In person there's romance and effort, time, I feel absolutely loved and cared about. When we're not in person it feels distant, friendly, vague, like a forced interaction, one sided really. Which was not like that previously.

Tldr: basically what I'm asking is does anyone else who has been in a similar situation know what to do about the disconnect that happens as soon as it becomes long distance again after being in person?
Disconnect with long distance relationship?
Post Opinion