Hello,
I have Emetophobia too. Its a lot more common than you think (I didnt realise this until a nutritionist told that she has a lot of clients with it).
For me, the sensation of throwing up emits similar feelings that I get when having a panic attack and I also get scared of losing control (another anxiety thing) so...it all comes back to anxiety.
I restrict what I eat a lot because of Emetophobia (feeling too full makes me feel sick which makes me anxious and etc etc). But I am getting better at dealing with it and as annoying as it is - it just takes patience and acceptance.
You dont have to be perfect. We are all mucked up in our own way. Breathing definitely helps