Why you always keep coming back to it, is because it's an addiction. As you probably know by now, you have subconsciencely trained yourself to cut when something upsets you. Now you don't know how to handle things w/o cutting. I don't know exactly when it will end..but keep trying. You can outdo this! You CAN win!
The only thing I can think of about the scars is scar reducer cream, I'm not sure if it'll work, but its worth a shot. Cover your whole arm in it if you have too. Also, If they ask, it doesnt really matter what you say because no matter what, they are going to think what they want. It's none of their business whats on your arm.
I hope everything gets better for you.
“Some days even my lucky rocketship underpants won't help.”
-Calvin & Hobbes.