Breathless in Bed
When I masturbate, I find that my orgasms are much, much better. I only do this when I'm by myself, never with a partner. But my question is, can this hurt me somehow? Like, depriving oxygen to the brain and so on?
When we hold our own breath by simply inhaling and refusing to exhale and take in more air, the body usually automatically stops us from doing this before we pass out. A few people can hold their breath until they do pass out, but once they are unconscious, their brain instructs the body to breathe.
What you're doing right now could only hurt you by giving you a ringing headache. If you aren't experiencing any pain afterward, I don't see a problem with what you're doing to enhance your orgasms. Many other people have found that holding their breath makes them feel more excited and creates stronger orgasms.
But I would caution you against letting another person choke you or using a rope or other artificial device to cut off your own breath. That takes you into dangerous territory. A chokehold can injure your spine or deprive your brain of oxygen for too long. And autoerotic asphyxia, as bondage-to-the-point-of-unconsciousness is known, has killed far too many people. The usual practice is to create a complex arrangement of rope that is supposed to loosen up and allow the subject to breathe as soon as he or she has passed out. But such arrangements often malfunction, and keep pressure on the unfortunate person's throat until they expire.
It would be safe for a partner to put their hand over your mouth for a few seconds. But it sounds like you would rather keep this technique for your private enjoyment. It's a clever discovery, and I hope you have a lot more fun with it.