The last few times I had sex, the condom fell off. It got me a little worried about condom size, so I masturbated with a condom on to see what would happen. It was snug, and didn't slip off, no matter how hard I pulled at the tip, but it did roll up a bit when I was masturbating. Then again, my hand wasn't exactly moist. I also did some measurements, and the circumference is about 5 inches, and about 6.5 inches long but it was difficult to stay hard while measuring. From what I can gather, this is pretty much average. Why does it keep falling off then? am I doing something wrong? Do I need a different condom size?