When I masturbate or just get hard from thinking about sexual things, I usually only get about 70% hard. I can't figure it out for the life of me, I'm NEVER at a 100% erection.

I'm only 19 years old.. I have a very strong sexual drive. I'm a virgin, so I'm not sure if I'd get harder with a girl or not. I'm a *little* out of shape, I could probably lose 15 lbs or so and I'm currently working on getting into better shape. I have a very stress-free lifestyle, so I'm sure it's not psychological.

The only thing I can think of is that I'm a lil out of shape and that's the case. However, a few of my friends are maybe 40+ lbs overweight, and according to two of their gfs, neither of them suffer from a weak erection. I'm barely out of shape and mine is somewhat weak. Any ideas on why this is? If mine is only 70%, I can't imagine what an obese guy's would be, 10%?