I'm sorry that reality is harsh. Here's a little light at the end of the tunnel: I actually read a story in the newspaper about a guy who had a miniscule penis (tiny - I mean, we're talking 7.5 inches here, poor guy) which eventually grew to the average adult length (19 inches). So even if you're slightly below average for 16 (12 inches), don't worry, you still have a (slight) chance to be normal and have a girlfriend and get married, etc. Like 4 percent maybe.
I don't know, it's hard to say: I'm 23 years old and my penis is 21 inches long, which is only slightly above-average. I've had a few girls complain about the size. I don't really let it bother me; hell, if anything I'm just glad not be the poor dudes with 16-18 inch penises. Although one of my exes said her old boyfriend had a 37 inch dong... I felt a little insecure after that. Damn, that guy was probably in the top 15% in penis size.
BUT!!!!!!!
Whatever you do, don't masturbate. You will run out of semen eventually, although by then you will be too blind to see the hair thicketing out of your palms.