Hello, I’m Christian And I’m 16 Years Old, A Couple

Hello, I’m Christian and I’m 16 years old, a couple of days ago I’ve slept awkwardly and two days ago I’ve started to have pain in my ilium/iliac crest/ hip area. It doesn’t hurt when I lay down/stand up in a certain position, but when I’m standing up/sitting down for a long time the pain returns, I have no signs of fever of swelling of the region. What is occuring to me and what can I do to resolve this issue? Thank you very much.