Andrew,
these are stretch marks. they happen when you put on a few pounds or when you have a growth spurt. They will always be there, but the redness will eventually fade. try some shea butter lotion to speed up the fading process.
Sorry, a bit of extra information in case its helpful. I do sit at a computer for many hours doing my college essays, watching movies, playing games etc. but I'm not sure its what causing it since the lines are straight up and down rather than horizontal. Also the lines are a bit indented as they fall slightly below the skin around them. I smoke Marlboro Smooths and live on a college diet :P lots of ramen, mac, pizza, etc. I also drink alot of soda to keep focus on my work. Thanks again.