Some people don’t like communicating via text/message, others aren’t good at small talk and only message when they feel they have something important to say. Some people aren’t good at initiating interaction.
When he’s working he might just be thinking about work and nothing else.
As others have suggested, speaking to him about how you feel and listening to his perspective might be a good idea.
I love company but when I’ve spent a period of time with others or my partner I sometimes need a couple of weeks on my own and the people close to me know and understand that.
You’ve said you’re insecure, what do you think might be behind that?