I'm also shy and appreciate you sharing that. What I want to share with you is that even people I know who aren't shy at all, some of whom show their naked bodies off every day and see hundreds of naked people each year, still have worries about how they measure up. We live in a world where "normal" is used as a yardstick, and from the moment we're born (even before) we're told that we should be worried about how big or small, flat or bumpy, smooth or hairy different parts of our bodies are. It's one of the hard things about living in this world.
But back to your porn star penis question. The first thing you need to know is that much of what you see in porn is staged, and comparing yourself to a porn star is like comparing yourself to a Hollywood actor in a movie. Check them out on the street, they are much less shiny and off screen they are a lot smaller.
In terms of penis size some male porn stars do have larger than average penises. It's one of the ways they get work. But many others use tricks to make them look larger on camera. I promise you that with the proper lighting, make-up, pubic hair design, and camera angle, your penis could look like many of the porn stars you see.