How to know if someone blocked you from sending them a iMessasge and texts?

This guy work with and I are been texting since July 5. He asked for my number and would text me first. When I send him a iMessage from my iPod Touch to his iPhone it just says delivered. He usually reads my messages. If it just says delivered does that mean he didn't block me? A coworker sent him a text and he replied to the co worker but didn't answer mine.

Added (1). When I text him from my phone (Samsung illusion Android) it just says that the text was received. He works 2 jobs and helps his dad around the house.

You can't tell if they blocked you, but you can tell if you blocked them by going to iMessage settings and then scroll down to block.