Guy best friends

How do I politely tell a guy who is just a friend that he messages me too much without being a bitch about, he literally only texts me and “says hey bestie I just want you to know I care about you and I worry about you that’s what why I’m checking to make sure you’re ok” literally EVERY MORNING! HOW DO I MAKE IT STOP!!! I’m not into this guy at all, and he knows that I have a boyfriend because we all three work together. And the other day I ignored his messages and he then texts me as his brother claiming he got into a car accident. I’m so frustrated but I don’t want to alienate him because we work together.