Friend/Coworker is acting distant and I am not sure why?

Anonymous

Let's call my friend Jay, we know each other from school and work in the same place (but separate departments). It started the first week of January. A few of my friends were getting together for my birthday and Jay was super pumped at first. I texted him a couple of days before just to make sure he could still go, and it wasn't until the day before that he said he can't make it due to a "family thing." We've been friends for two years and tell each other everything so I was surprised when he didn't go into detail about what this family thing was. I was surprised, but I didn't think too much of it and didn't push it. He left on a trip with his girlfriend that same week, and when he came back, he had changed:

- He unfollowed all but four of his close friends and started following all of her friends.
- Quit his band and joined hers.
- Stopped hanging out with us.
- Doesn't respond to our text messages, keeps saying "Sorry, a lot of people have been messaging me lately."

Now when we are at work, he doesn't mention his girlfriend unless someone else does first, which I thought was weird. But then he said he isn't taking this relationship seriously so I figured whatever. During work, he'll update me about his life, talk about future plans, etc. But once work is over, it's like he's trying to get away from me (I'm not clingy by the way, we only see each other like twice a week at work).

Yesterday, he said hi to me, like always. Later on I needed a tool from him. When I asked him for it, he said he would bring it over to me in a little bit. An hour or so later, I saw him walk by, then realized he actually left. I called him, then texted, to see if he was at least coming back but no answer. I was mad at first because I really needed that tool, but got over it because I figure something happened or he forgot. During my lunch, he was posting on Instagram so clearly, he had his phone and just wasn't responding to me.

So here is my question: Should I ask him what's up?

Friend/Coworker is acting distant and I am not sure why?
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