I am a guy, totally into the same thing. The only difference, i am totally submissive or better said masochistic. Don't worry, i think your fantasy is totally ok. You wouldn't believe how many people are out there with the same fetish.
For my part i love to imagine, that a woman or more persons overpower me and start asphyxiating me in any way. Choking, drowning, strangling, hanging, suffocating etc. etc. , it's all part of it.
Am i sick? Well, i asked that to myself many times. Just like you, i cannot talk to anyone about that matter. But what can i do, it just turns me on. It's too hard to resist.
Actually i am surprised that you are more on the dominant side. Most women seemingly are masochistic. It's seems seldom for women to actually asphyxiate a person. Well i might be wrong. Maybe there are many more out there than i can imagine.
Wow, the thought of you being a dominant suffocator just turns me on right now. Well ok, my advice: Just enjoy it, don't think of yourself being sick or so. For me actually it's so nice to see that i am not the only one on this planet with this fetish.
Nice meeting you here