I know that you want to make her happy but when it comes to relationships, you must keep in mind that you have to be happy too. If you aren't ready to have sex, then you aren't ready to have sex. Don't force yourself for the sake of other people if it's going to make you uncomfortable and unhappy. I mean unless your heart is really set into making her happy without any regards to yourself, then I suggest that you think about yourself first in this situation.
Also if she is hurt just because you don't want to have sex with her, then she isn't being very considerate to your feelings. If she truly loved you and cared about you, she wouldn't feel hurt for you making that kind of decision. Yeah she might feel disappointed and that's totally normal, but she wouldn't pressure you to do something you don't want to do. But if something like this is what hurts her and your relationship, then your relationship with her was never meant to be. Her sexual needs aren't being met and your happiness level isn't being met so it's best for both of you to find different people who would make each of you satisfied. And if that's the case, know that this isn't your fault or your girlfriend's fault. Just know that you two are different people who require and want different things that each of you can't give each other and that is perfectly fine.
So what should you do? Tell her you don't want to have sex because you aren't ready yet. Don't be ashamed of that. I know that you might think that because you are 19, you should technically be ready for whatever but we both know that that's BS. You can take as long as you want to be ready and there is no age when you have to have sex. You can say to her that once you're ready, you would like to have sex with her but only say that if it's true. But, like I said, if she gets hurt by this, then suggest to her that maybe it's best that you two saw different people.
