Self-injury does release similar feelings to that of stimulation in some people so I wouldn't say that it is anything abnormal at all , however SI can be an extremely dangerous habit as it can be extremely addictive and many people end up depending on it, and needing to injure themselves more severely to get the same excitment.

If possible I would suggest that you try to find safer ways to experience those good feelings. This might feel good now but can be dangerous.