How long have you been dating him? It sounds like this is the longest you have not texted/talked? Four days is not that long that I would automatically decide he has broken up with me. People need different amounts of space and time to work through things in their lives and no one shares everything. I've been married 25 years but there are times my husband is quiet, thinking things on his own mind through or I am not so keen, etc. It does not mean it is about you or the relationship! Sounds like working a double shift took a lot out of him. I bet he contacts you maybe by tomorrow/Sunday evening. Sounds like he just wanted a bit of space for the weekend.