The reason you're afraid of throwing up is because you have Emetophobia.
The Emetophobia is a common phobia that a lot of people have that make them fear or be afraid of throwing up and it's nothing to be embarrassed about.
All people have different phobias about just about anything even though they may not admit it.
My sister has Emetophobia which is the fear of throwing up and she really looks frightened when she's about to throw up or has thrown up.
If you do need to throw up though you should do so because your body is wanting too and needing to get rid of that vomit that is in your stomach.
The sooner you throw up the better.
When I have a stomach ache and feel like vomiting but cannot on my own I do make myself vomit so that I feel better.