My boyfriend has been calling me 'yo' lately?

I feel like he is friend-zoning me. Things haven't been great between us lately. We don't fight, but we're definitely growing apart and we haven't even had sex for two months. To be fair, he's been away for a few weeks, but we didn't have sex before he left. He is out of town for a job until the beginning of November. That's why I am not asking him about this, it feels like a face to face conversation. Ever since he has been out of town, he calls me 'yo' in all of his texts.

Last night he texted me: "Good night yo!"

And he used to call me affectionate names. I tried spicing things up before he went away, but he told me he was too tired. I get the feeling there is a break up coming up, because it feels like he is withdrawing from me. We live together, and have been together for three years.

Also, he calls all of his friends 'yo' including all of his female friends. I always thought when he called his female friends 'yo' (one being my best friend) was his way of friend zoning them. One girl had a crush on him, and he went out of his way to say things like "Thanks yo," or "That's pretty cool of you, yo." whenever she did stuff for him. Now he is doing it to me.

Does it sound to anyone like my boyfriend is friend-zoning me?
My boyfriend has been calling me 'yo' lately?
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