What to do...DA potentially

Before you analyze his attachment style, is what he's said he is willing to offer in line with what you want? He sounds like he's set on a casual but steady hookup. Is that what you're looking for as well? If not, you may want to bail on a guy who already stated he's not interested in making a relationship or a partner a priority. Even if he is DA or not, he's happy being single for the time being, and that should be respected.

How long have you been seeing each other? He seems like he is happy to enjoy your company when it suits him. That could be DA or it could just be a not as into it as you are guy. I can understand not wanting to leave a dog alone..and one not great night is just that. That happens.

It sounds like you are frustrated having to do a lot of the initiating and like you want someone more emotionally available and enthusiastic.

If you stay in a relationship with someone who seems hot and cold or emotionally stingy for whatever reason it is going to make you more anxious over time.

Yes. I totally get it. It is exhausting and doesn't make sense. Why is this guy not leaping for joy and making a big effort? Especially in early buzzy days.

One thing I learned for sure is people tell you who they are right away and you should believe them.

So you can talk to him and say you want him to make more of an effort and be more enthusiastic. But you can't convince someone to feel differently IMHO....

This is what happens. There’s this expectation, without actually saying anything, that every intimate interaction is working towards something bigger. He should be this, he should be that.... this is a time to look at yourself and your motives. I was in a situation recently where sex was used as a manipulative tool, and while it may have been different in my 20s, in my 40s, no amount of sex is worth the grief of being manipulated.

I am DA. It sure looks like you are trying to make a Relationship out of Friends with Benefits. This will Not Work.

If a DA man is having sex with you, but not acting like he wants a relationship, but says he really likes you , it means:
The Liking:
He wouldn't have sex with someone he doesn't like, or even someone he just tolerates. He won't spend time around ANYONE he doesn't like because that's how DA are- solitude is preferred to poor company. So yes, he likes you. This means NOTHING other than he finds you to be decent company. It does NOT imply relationship potential beyond the meetups you are initiating for sex or whatever else.
The sex:
Is sex. He wouldn't have it with somone he doesn't like, see above.
The not acting like he wants a relationship:
Speaks for itself.

You are AP? Take a look at what you are doing here, you chasing an unavailable guy. I would never cheerlead you into asking for what you need, thinking you're co creating something, because thats your own narrative. It's an AP narrative happening with a person who isn't sharing your narrative. I don't know if he is DA at all. He is just a guy who isn't pursuing a relationship with you and believes you signed up for casual sexual with him because you did. Did I understand that correctly?

Go find a man who wants to co-create if that is what you want, but don't try to move casual sex to a relationship. Or you end up here talking about him being possible DA and leaving your AP out of the conversation, and you get your feelings hurt in real life because you're loving a fantasy there and here also.

Also: what mrob said.

If you agreed to go casual, then keep your word. Go casual. Don't change the script. It won't work for you. However, it will work for him the whole time you consent to having sex with him while carrying out the relationship in your head and here as long as you don't bother him too much about it. That's not what you want, right?

I'm not at all saying DA are horrible. I'm saying.... what you see is what you get. There is really no blame here, he's accepting what you are putting out and you are accepting what he is putting out by participating. From what you've written here, I can only see that you are participating in a FWB situation.

Oh, I took  the phrase "casual relationship, not serious " at face value.  
The popular meaning of that is a non-committed (not serious) relationship which may or may not be exclusive depending on agreement, not intended to progress to something serious.

Either way, what you see is what you get. All my original points remain and may or may no apply, but talk about something like this potentially ending in marriage is just odd to me, personally, and I would see it as manipulation. either because he knows what you want and needs to give you some hope to hang in there (which is horrible behavior) or he's a really conflicted guy and possibly not DA, maybe another attachment type, who knows).

Back to the basics: what you see is what you get, I'd encourage a heavy focus on the fact that you are AP and unhappy with an unavailable person.  Best to you! 

Thanks I appreciate your input. Focus back on me for sure. We are meeting tomorrow to discuss where we go from here. Think a split might be on the cards.