As BB and Kiya said, you do deserve support. Any way of hurting yourself is SI whether it leaves a scar or not. And snapping a rubber band HURTS!!! Stay strong. Have you looked at the times when you snap the rubber band (and scratch)- is it when you start to have 'undesirable' thoughts come into your head, or do you do it subconsciously? If you can figure out the main times that you are doing it then you can try finding alternative things to do that aren't involving SI...Always easier said than done tho!
And you are right, snapping a rubber band is used by some ppl to stop thoughts/flashbacks etc;- when an unwelcome thought of any kind comes into your head you snap the rubber band to remind yourself to redirect your thoughts.