How do I get the courage to post my fan fiction?

I’ve been obsessed for the past few months with a story I have on my head that I just went up and finished writing 30+ chapters of it in two weeks. I felt like I couldn’t stop myself from writing even though it was late at night or I had work to do. Now I’m even starting on the next book (in my mind I think the entire thing spans 3 books). It’s a fan fiction of my favorite Harry Potter character and a female OC. I planned to only share Book 1 once I finished Book 2 but I’m having such a hard time on the structure and pacing pf the second book that I wanted to have some motivation from knowing that the story will be liked by people. Because it feels like a lot of effort for nothing. My problem I would say is that I’m too scared that people won’t like it or worse ignore it. So my question is - how do you get over that fear? Also how do you get a following for people who would likely be interested in your story? Looking for advice. Thank you.🙏