I hate being such a jealous person and I'm feeling pretty guilty about it
How miserable for you. Do you plan on admitting to other people that you're jealous?
I might get in trouble for it or people would think I'm a silly child
We can't control our feelings of jealousy but we can work on it. Look at the reason why you're jealous and try to resolve it.
I'm an adult and I know what I'm doing unlike a child. I can control my jealousy.
That's great! As long as you're controlling it you shouldn't feel ashamed for a fleeting moment of jealousy. It's pretty natural.