I am 22-years-old, and as of a few days ago my penis is completely soft. I cannot get an erection and find it very difficult to flex my penis. Nothing like this has ever happened before and I am really scared. There is some pain near the base of the penis (under the testicles) when I try to flex it. It's almost been a week and I am freaking out. What could it be? What should I do? Thanks.