Welcome to HW! First of all, I think it is really admirable that you are looking for a safer way to deal with stress in your life. I had a counselor once who recommended ice cubes. You can use up to 2 ice cubes at a time but shouldn't do this more than once per hour. As long as you limit it to once an hour it is totally safe. Different people prefer to hold the ice in their hands or rub it on their arms or legs. Whatever works for you is fine. ;)
You can also try running. Even if you don't get a "runner's high" the first time, keep at it. It wasn't until I started running more than 3 miles that I got the benefit and that took some time but once I got strong enough I was able to go running whenever I felt really scared and it would make me feel so much better.
But Karen is right in suggesting counseling. Long term, that is your best bet. One type of therapy that is designed specifically for people struggling with self-harm is Dialectical Behavioral Therapy (DBT). You can try googling DBT & the name of your town or nearby cities to find a qualified therapist in your area, but to get you started there are some self-help resources here: www.dbtselfhelp.com/
. They are not a replacement for therapy, but can help you for a while until you can get professional help & might help you identify with the kinds of people who generally benefit from DBT.