Everyone is different with regards to stretch marks. Some guys are prone to them more than others. Could be a genetic thing too, I believe.
I got one early in the game right where you said you got yours and never got anymore after that!
However, (insert gay jokes here), I mosturize every time I get out of the shower to protect my skin and help with elasticity.
There are some strech mark products out there though, but buyer beware. Lots of dissapointed customers man...