I am only 18 years old, and have been sexually active for a few months now. Sometimes when I have sex with my girlfriend, i will just lose my erection midway through the act, this usually occurs when we change positions, or I get distracted and think about something else. I am also uncircumcised, and sometimes the condom slipps so that my foreskin is back covering the head (you're supposed to unroll it before sex), and that leads to basically no sensation and that = my penis going limp. Now this shouldnt be a problem for someone my age, but this has happened on more than one occasion, and I could really use some help!!