From your description, it doesn’t look like anything happened “wrong.” But that doesn’t mean you are being ridiculous. You’re engaging in activities designed to unleash powerful emotions, so it is never ridiculous to feel those emotions after a scene. You are also unleashing powerful chemicals: endorphins and adrenaline. Playing around with them can be very rewarding, but sometimes it can be more than we can handle.
A lot of people cry after scenes. Sometimes it’s a cathartic release. But when a scene doesn’t give us the release we were expecting, the chemical crash can leave us feeling unpleasantly drained. It sounds like you are blaming yourself. I’m not going to tell you how to feel about the scene. You get to feel however you feel, and no one should tell you differently. But I will say that you are much better off calling things to a stop when you need to than trying to tough it out.
So how do you “help” this in the future? First, keep in mind that you’re still in the early stages. You’re experimenting! That’s a lot of fun, but not everything is going to proceed exactly the way you expect it to right away. This isn’t a failure. It’s a learning experience. It may even be a training experience. You can’t expect your body to go from zero to 60 right away (and a partner who expects you to be able to do that needs to adjust their expectations).
Also, you can reflect on your crying and your depressed feeling. Just because they happened at the same time doesn’t mean they happened for the same reason. The crying might be coming from the endorphins while the depressed feeling might be coming from the adrenaline crash. This means that they might not always occur together. It also means that they might just be physical reactions and not about the content of the scene itself. In the future, you can try to separate your feelings about the scene from your body’s readjustment to normality. It’s your feelings about the scene that matters (unless your readjustment is so severe that you don’t want to keep going through it).
Lastly, would you prefer that your aftercare started immediately? Maybe your husband should have stayed with you for a bit before leaving. It’s completely fair to ask for that, especially after needing the stop word. Like I said, the crying might have just been a physical reaction. But even still, you might have felt better about it if he was there with you. Or maybe not. Only you can answer that question for yourself. But it’s something to think about.