I get understand what you mean thinking about natural thing as sex , even though it's very much is so,
there is something paradoxically weirdly gross about things to do with our bodies, bodily emissions ect,
I really think as you are obviously uncomfortable and put off the idea of that sexual practice,
hardly Surprising cause of your past experiences ,
let's face it , that kind of sexual practice is like sexuality equivalent of marmite, either love it or loath it,
I think it's really Disrespectful of them,
they thought it was ok acceptable for you to participate in this sexual practice knowing their personal hygiene was rank, skanky as fxck too,
Oral sex just like any other sexual practices should be based on mutually pleasurable and respectful intimacy loving relantship,
I wonder whether tantric sex practices more emphasis on sensuality of sexuality ect would be enlightening and beneficial for you?
Karma sutra book springs to mind too.