What you have is called "emetophobia." (The fear of throwing up) There are a lot of people who have this, so please know that you're not alone, OK? You're not some kind of weirdo for feeling this way. There is help for those who have this disorder, but you absolutely must talk to your parents about this. As with all phobias, there is no magic pill you can take to make it go away. You need to talk to a therapist to figure out WHY you are afraid of throwing up..........and trust me, there IS a reason and once you figure out what that reason is, you and your therapist and your parents can work on overcoming it. You're obviously an intelligent young person since you wrote to us for advice, so I have no doubt whatsoever that you will be able to beat this.
If for some reason you don't feel you can talk to your parents about this, please talk with the nurse at your school. They are the best and will help you through this.
With a little work and understanding on your part, you'll be able to put this behind you.
I know you'll be just fine.
I have emetophobia myself. I am terrified of it. But after some counseling the fear doesn't control my life anymore. And I've actually thrown up a few times in the past 5 years. It was scary but it helped me fight my fear so to speak. It is possible to get through it. I'm still scared of it. But I've made so much progress. I'm no longer scared to eat..I can eat in restaurants...and do so much that I couldn't do before because of my fear. My next step in the next few years is pregnancy. I swore I'd never have kids because I was afraid of morning sickness but now its becoming a possibility. Talk therapy helped so much. And exposure. It was hard but you can overcome it. Start with asking parents, school counselor etc. They can help you. Good luck. You can get over the fear with some work with good doctors and support from family.