To be honest, I think subspace comes along mostly with pain. I wouldn't want to rule out something else since I'm no expert on this, but I believe the reason why some are so adamant against BDSM and reaching subspace is because it is technically the body's way to shut down and protect itself from pain. It happens a lot with abuse victims, so it really isn't surprising that you "disappeared" with your ex. Therefore, your body isn't going to shut itself off from pleasure with your husband because it doesn't need to.
With that said, I will say that while there are certain similar symptoms to subspace, everyone reacts differently, and knowing how you react is an important safety measure to plan for. For me, I won't play with anyone I don't trust explicitly, whether I'm meeting a sadist/Dom for ONLY a beating, or if I'm playing with a sadist/Dom I plan to be intimate with. I won't let myself be vulnerable unless precautions are in place, meaning we have a clear understanding and agreement of limits, what I'd like to get out of it, and what he'd like to get out of it. I also don't play with anyone I've never seen play before, and I ALWAYS do my homework. That means I've talked to people who have subbed or bottomed for them. Anyone who is reputable, who has nothing to hide, will encourage this anyway. The sadists and Doms I have played with, or who are my current partners, are men who have been in the lifestyle a very long time, who have a lot of experience, and have more positive reviews than negative (because let's face it, this is a subjective sport - there will always be someone who didn't have a great experience with a partner, and that's the risk).
The reason why I need to go through these steps is because the person I have a hard-core scene with, is going to see me at my most vulnerable, and will need to be able to respond appropriately so that I don't get hurt... emotionally or physically. My subspace is sort of different than others' and can sometimes shock or throw off a person if they aren't ready for it or know what to do with it. As a little, I get even more little in subspace. I cry a lot, which for some can be a major turn on, and for others it can be quite uncomfortable to observe, but it's a very necessary release for me. I need my partners to talk to me gently, but carry on in their demented, evil, and sadistic ways. One of my favorite partners who I only play with a couple times a year looks like Santa Clause, is a very gentle and nice older man, but is as sadistic as can be. He really enjoys the emotional element of our play and likes to give me the "daddy like" care in my distress. After any session, when I am in true subspace, I get super cuddly and need to be held. There is a lovely, euphoric, almost drunken, sleepiness that comes over me (and I think most people, actually), which is also why I always ensure I have someone there who will protect and take care of me, and who will get me home safely (if I'm not already home).
Obviously if one is new to this, they may not know yet how they are going to respond, or they could be going to a subspace without recognizing their own personal, unique symptoms. In hindsight, when I was starting out in the community where I live, before I fully understood my subspace, I was dating and playing with a Dom who was really into the Master/slave dynamic. So when he’d beat me, he’d treat me like a slave, which was REALLY SCARY for my inner little, as you can imagine. That relationship didn’t last very long. He was also a bit new and didn’t pick up on the signs I was giving him, which unfortunately led to one last dangerous scene for me. I didn’t realize this until nearly 6 months later.... when I played with my Santa Clause partner (above). I definitely don’t regret anything, and to this day we are still friends. To me, this is all about me learning more about who I am. I
am the main character of my life story, as are you to yours.
Wow, lots of tangents here, but sometimes the teacher in me takes over and turns simple questions into lessons. Sorry, Ella! I hope you were at least able to pull what you wanted from this reply.