Eating any sort of "fat foods" stress me out?

So I wanted to try to a ketogenic diet because I want to lose 20lbs. amd it's seriously stressing me out. I haven't let myself eat high fat foods since 9th grade. And I've beat myself into having a strict diet.
But now I'm looking to change and it's awful. I made myself chicken and vegetables. I cooked the vegetables in oil which I rarely do because I steam everything, and I did the same with the chicken. I just sat there for 5 mins looking t my plate. I hadn't even eaten the food but I already felt kind of gross and greasy. When I actually started eating I kept feeling sick and slightly nauseous. It made me feel just disgusting. 3/4 of the way I just started gagging and crying. It was just really weird. I've so rarely eaten meat over the years that I'm freaking out.
Now I really don't know what to do. That meal was so ridiculously stressful and hard for me to finish. I don't know how I'll be able to make this transition to high fat?
Eating any sort of "fat foods" stress me out?
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