it's been quite a while since I've done any posting at all here...last time I tried to start up again my life immediately went nuts. But i'm trying again, with a question, or atleast something to get off my chest.

I've just recently started having sex with my ex-boyfriend, in a strictly 'just friends' way, and it's been developing into a BDSM relationship at a pretty quick pace. he knew from when we were dating that i was submissive, though his dominant side has been longer in coming out. After we broke up we had the obligatory not talking phase, and then slowly started being friends again. Eventually it got to the point where I can tell him more than anybody else, especially in regards to my sexuality, as I started discovering my masochistic side in addition to the sub tendencies I'd already known were there.
Long story short, we started having sex, agreed that it was solely as friends and we were just having fun.
Now much to my delight he's showing himself to be quite the dominant. The sex is fantastic and he's learning how to push me & make me squirm entirely too well.

The dilemna I'm having is that we're still officially 'just friends', and outside of the bedroom we act that way. We're good friends, but aware of the space between us, the difference from when we were dating.
But during and after and to a lesser degree before sex/play the interaction changes drastically. When I've had sex with frineds in the past, we've still acted like friends during sex. With this guy, and this sex we act like a couple. The difference seems subtle, and possibly all in my head (though I don't think it is), but I'm still aware of it.
During, he's as demanding & sadistic as I could ask, but has also proven that he can drop that in an instant if I need comfort; at one point this weekend I got kind of freaked out & froze up, I'm still not sure exactly what caused it, but he noticed right away and stopped and just held me until I came back to myself, didn't start asking what had happened until I was settled, and was gentle & careful about coaxing me back into play. Which I ended up enjoying immensely; some of the bruises will last a few days.
Afterwards, we cuddle & laugh & exchange silly kisses, and generally do a good impression of more than 'just friends' until we get up & dress, and then it's back to that space between us. And I'm not sure that I can keep dealing with that transition. Granted, I haven't been doing it for very long, but it's jarring & I prefer how we are when we're not being just friends.

The problem is that as far as I can tell he's good with being 'just friends', though admittedly I probably give that impression too, we haven't talked about it since the initial conversation after we found ourselves in bed together, and I feel like I'm falling for him again. I know that I can do sex without a romantic/emotional attachment, I've done it in the the past, but this is my first D/s experience, so I don't know if the way that I'm feeling now is a result of of the higher emotional stakes involved in this kind of sex or if it's a result of this guy. Either way, what do I do now?

I don't know what I'm looking for in a response, but I needed to get this off my chest.
My apologies for any incoherencies within, I kept rearranging sentences trying not to be longwinded, if anything doesn't make sense just ask