Just go for it man. I didn’t ask anyone to be my valentines this year because I’m going to uni soon but I did give a girl a nice note because I felt like it was right. If you feel like it’s right, then it’s probably right. Don’t overthink it.
I think it all just comes down to confidence and not being afraid of getting rejected. Asking a girl out is a win-win because if you get rejected you gain more experience. And by getting out of your comfort zone more you won't have as many missed opportunities that you'll regret later in your life.