How old are you? Are you still a kid? If you are, maybe you are still young, your penis hasn't fully developed yet.
常常「褪」翻落去 is because your 包皮 too long, and your penis is a little too short.
Since you can 反起, so i dont think you need to 割包皮.
What about when your penis stands up? 包皮still 「褪」翻落去?
If you think it bothers you a lot, then you should go see doctor.
Actually, its not a big deal.
And it doens't effect on having sex.