Self-harm is a new experience for you and so I would really like to recommend that you try and stop self-harming as soon as you can. It is an addictive thing and it could soon turn into a bad habit. I understand that you say that it felt good but it isn't healthy for you and is, in effect, damaging your body. As it's damaging your body, I'd suggest that you look for a safer alternative (you could always check out the alternatives list for some ideas) - it may feel good now, but if you hurt yourself badly, would it be worth it? There are so many safe alternatives, so please check them out.
You shouldn't have to inflict harm upon yourself in order to deal with things or feel good, Erika. I'm glad that you had a really good day with your friends. Do you think that perhaps you could talk to one of your friends when you feel the urge to self harm or when you're feeling bad? It's good that you're socialising and still going out and having fun. It's also good to have a 'rant' to people sometimes and I'd like to encourage you to talk about how you're feeling with people as it's good to have some support and someone you can turn to.