Why am I terrified of puking?!

I am the exact same as you, literally. I am nineteen, and I haven't thrown up since the 3rd grade. I have been terrified of it for as long as I can remember.
We are what is considered to be "emetophobics". An irrational fear of vomiting/vomit.
There is no cure for it really, but you can take measures to make yourself feel better. I went to the extremes of locking myself in my house for most of my teenage years. I was able to do this because I was homeschooled. Whenever my parents would go to the grocery store, I would stay in the car. I always washed my hands. I would wash my hands to the point where they bled. And I changed my diet. I became a vegetarian, as meats tend to be more dangerous when it comes to bacteria, especially if undercooked. I no longer eat out at restaurants, and I refuse to eat creamy foods/sauces like mayonnaise.
I find what helped me is exposure. There came a time when I had to go out and get a job, and at first it was difficult. Because I was exposed to germs, and when working an eight hour shift, it became difficult not to use the bathroom all day everyday. So with this exposure, and having no choice but to be amongst the germs and such, I got better. I still have my flare ups, where I worry all the time, especially if I eat something that I think tasted suspicious, or might have been expired. I also tend to freak out if a family member falls ill. But all in all, I am better than I was. So what I suggest for you, is to try and go out and expose yourself to things. Just be sure to keep yourself clean, to avoid falling ill from stomach bugs. Spend time with friends. Just do anything that gets you out of the house, and keeps your mind occupied. Even if you start out small and work your way up. You gotta try, and you can do it :)
I hope this helps. I know how difficult severe emetophobia can be to deal with.

i think its pretty normal since im afraid of puking when im sick even though i know it will make me feel better i avoid it even if it makes me suffer for more time sooo i think it is a normal thing dont worry too much

It's a phobia, the question is, why would you even have it?
Hmmmm. look in to it farther.

could be a puking phobia, that′s normal

It's just a phobia or something. No one really likes throwing up. I think it's kind of scary too.