My guess is that M is perceiving this very different.
From your viewpoint he is pulling away, not there for you, not committing, withdrawing, this is a test of the relationship and possibly a sign that everything is falling apart.
For him I'm guessing none of this is going on, he had a great weekend with you and has now been taking some time on his own for a couple of days for whatever reason. I would bet he's shocked that this is all going on in your mind right now.
I'd recommend you find a calm and stable place before deciding what to discuss with him. See how things play out. See what he volunteers without you any type of questioning. See how he interacts with you over the next couple of weeks.
Yes, in a relationship you can express your desires. But I think you'll be more productive if you are less escalated when you have those conversations. And it might be that things play out where you don't even need to have a conversation, things might just work themselves out. You wonder why things start to go south for you, I'll bet they don't as long as you don't hit the panic button.
Me:38 XW:38 T:11 years M:8 years Kids: S14, D11, D7 BD/Move out day: 6/17/14, D final Dec 15