How do I handle obsessive thoughts that feed into my phobia?

I developed severe emetophobia (fear of vomitting) as a result of obsessively worrying about it. I can pinpoint the exact moment it developed: I was 16 at a family gathering, started feeling nauseous, and began worrying about getting sick. The worries continued even after I went home, as I still felt nauseous, and persisted for the next few days... Except, it wasn't just a few days.

I'm 23 now, and I never did get sick, but every single day I worry about it and can't even leave the house without it spiraling so bad I almost pass out from panic.

There are a few things that help me manage it, your average "if I do X, it will be okay" stuff. I carry a plastic bag if I go out, which helps keep me from spiralling. During car rides, I talk non-stop to distract me from it and minimize nausea.

What I'm struggling with are thoughts that CAN'T be mitigated by "doing X" behavior. If I'm sitting alone in my room and start worrying about it, it's very difficult to handle the spiral. Those "assess the thoughts and know they aren't true" don't do much, because I have another thought that likes to chime in and call me a liar. Thinking about how I would handle it if I DID get sick are dangerous territory, because it leads to me wanting to let it happen to get it over with– which I'm scared will lead to me getting sick as the "doing X" solution to stop obsessing over it. Which I'm fairly certain is NOT healthy.

Do you guys have any advice on how to handle this? It's been, what, seven years of this? I'd like to be able to live my life.