I'm afraid of what she'll think about my penis size?

To be honest, I know there are a lot of questions like this, but I want specific answers for me. I always get offered oral or sex but I always tend to refuse and just satisfy them with my oral skills. The reason why is because I'm worried about my penis size and what the girl might think. I tend to get worried if they'll gossip about my small willy or something. There's this girl I really like and she told me she'd give me a blow the next time I saw her as long as i returned the favor, which is in a couple days. My size is about 4.75-5 inches long in length and a little more than 5 inches in girth & I also don't last very long when I masturbate. I'm Asian and I'm 15 (don't want to be stereotypical here but yeah), so maybe girls would take that into consideration because I'm only 15. I refuse oral so much that's all I can really think about, is how it feels.Is anyone feeling/felt the same way? Please share your experiences if you have the same or close to my "size". Girls, would you think it's small if you were 15? Thanks a bunch.