My texts are not showing up delivered. Does this mean I could have been blocked?
No,

When a a user blocks a number on an iPhone and someone else with an iPhone sends a message, it appears delivered.  There is no way for someone to know they were indeed blocked.

Maybe the phone is off. 

http://www.pcadvisor.co.uk/how-to/mobile-phone/have-i-been-blocked-in-ios-7-who-blocked-me-ios-8-iphone-ios-9-3476005/