Just so you know, a lot of that -- deepthroating -- is more a set of expectations based on porn and other sexual entertainment than what what works for people and is mutually enjoyable for people in real life. Oral sex, like all kinds of sex between partners, is supposed to feel good for both people, not just one. So, whatever you do should be about what feels good for you and your mouth and throat, not just avoiding something you hate (choking). However deep feels good for you, that's how deep is right. Generally what makes whatever depth feel right is about what we're emotionally comfortable with, and how it feels to us, but also about how relaxed the muscles of our mouths and throats are.
Often when people think deepthroating is hot, what they think is hot *is* that the person giving it is choking and seems to be in pain or uncomfortable, or that it's hot to make yourself uncomfortable for a partner's pleasure. There's a lot to talk about if that's in the mix here -- anything from how to understand, negotiate and otherwise practice BDSM (pain as pleasure, effectively) in healthy ways to processing cultural ideas about how it's often considered hot for women, in particular, to be in pain from men. But I'm open to talking about any of that if you want to.
What you were feeling was most likely a bunch of "happy" chemicals we tend to experience in positive sexual interactions -- endorphins, dopamine, oxytocin -- and just feeling happy and satisfied. There's nothing weird about that.