I broke my ass (yes, it's PewDiePie reference)

I finally did it! I broke my record. In this video i managed to push 7,5cm in my ass. My next goal is 8,5cm. I truly don't know how to get there cause i also don't have much length capacity, and that seems to be harder and more painful to adquire to me personally. And more dangerous, and i really don't wanna end up in the hospital. if you have any tips on how to develop more length capacity i would like to hear it in comments.