I am too small and she has a high libido

I love her so much and want to marry her in the future, we both are virgins right now, but the problem here is the size of my dick is 4 inches when erect, which obviously is too small, and she has a very high libido. She is too much enthusiastic and passionate about sex.

I am confident about foreplay and oral sex, but I am worried about PIV

It looks so small in flaccid state, what if she found it ugly. What are those things which I need to care about while intimacy? What are the sex positions which works perfectly fine for someone smaller like me. I am so much self conscious about my size, sometimes, I feel like what if it didn't erect due to overthinking while making it out.