Starting Self-Harm

First of all, sorry for my english, it's not my first language

Well, I'm a teen, I don't do self-harm, or at least I didn't, but I think I'm starting to get into it. It first started with small things, punching a pillow or the wall or myself, banging my head against something hard... But I didn't consider it self-harming, I thought it was normal. Then a day I felt really down and I've tried to hold my breath to lose consciousness or to death or to drown me in the sink, but I failed and again I've didn't consider it self-harm but a suicide attempt. Then yesterday I had a breakdown when I was alone at home and the scissors were near to me. I remember I really wanted to see my skin opened and the blood unter it, it hurted me tring to do that but I couldn't stop scratching, it didn't matter the pain, I continued (also with my nails) until I've seen a little red stain on my leg but even then I couldn't stop. Somehow then I trew the scissors far and became enough conscious to write to someone and calm down a bit. Now I'm very near to enter in the loop of self-harm and the thing is that I'm not sure if I want it or not. Apart from the physical pain, I felt well doing it, and I feel like it's a good thing even if I know it isn't. I'm blocked between doing it or not doing it and I just don't know what to do. ANY advice from ANYone will be welcome. Thanks for reading all of this and for dedicating time to me and my problems. Thanks to all of you.