Augtan, It's good to have a place where you can just put it out there without filtering for what you know people want to hear you say. I can't say I have the same relationship with my ex, but then he's still far away and I don't have that kind of contact with him. He doesn't generally get in touch for anything other than asking for updates on our son, except the one time our son was visiting him (then he was chatty and flirty). And I don't get in touch with him unless I need to tell him something in regards to our son.
So I could claim to have set up really good boundaries. But that's BS, because at this point if my XH initiated sex I'd have a very hard time turning it down. Seeing as how the last time I've been intimate with anyone was with him before we got separated about 2 years ago. Being a single parent in a new town and working a lot of hours in a home office really sees to cut into the dating scene.
Having said that... I think you should be as honest with yourself as you are with your posts on this board. If you're like me, and I think lots of us LBSs on this board share this in common, you are still deeply emotionally attached to your ex and having sex with them only strengthens that attachment (in us, not our XH/W). Which means that although you may say you are not expecting this sex to mean anything as far as his desire to return to you, it is still going to hurt like a mother when he pulls away and signals or flat out says he doesn't want to commit to you.
I'm not beating you up for sleeping with him either. After all, we all have sexual desires/needs. But I wonder if it is really possible for you (us) to really not read anything into it. To not just open up the same wound. And how could you possibly give any of these other guys a chance to show that they're worthy of committed relationship if you're still reopening wounds with your ex? Well, you can't. But I also admit that it would take a Herculian feat of strength and stoicism to turn away from all the signals and crumbs tossed your way by the father of your children and the "normal" man you married, the love of your life, etc.
Frankly, I don't have that kind of fortitude. That's why I still fantasize about my XH telling me he's quit drinking and gone to counseling and wants me back. If it weren't for the fact that my ex was transferred away during our separation and my way of surviving the divorce proceedings was to cut off all communications and only talk to the lawyer, I would probably still be in the push-pull cycle of torture you are in. And, OK, if I'm being honest with myself, I AM still in that cycle of torture. It's just that the peaks and valleys are farther apart because we have so little communication. And I'll be completely honest with you and say, it's basically one long valley, with the occasional scary drop below sea level, and the occasional quit ascent to half way up. Right now, if I could have the drama of the push-pull back with my XH and it came with sex... I really might take it over what I have now.... except when I consider the impact it would have on my son as he gets older.