You "like" it because it causes your body to produce temporary hormones like a natural high temporarily relieving your inner turmoil. You've thought about it on and off but you've come this far without hurting yourself. What sorts of things do you do to help you feel better? A nice hot bath? A walk? Reading a magazine? We all have different things. Find that something you can use when you are going through urges and have it planned in advance so that you know when you feel like doing x you're going to do y.

You're punishing yourself and I'm not sure what the underlying reason is. You'd have to think about your sense of self worth and identity and what incidences, from childhood, school and adulthood have caused you to form your identity. Then think of arguments against it.

"Not enough to be classified as having an eating disorder" - that's a myth - you have one even if you've never officially been told that. Have you got any circumstances going on making you feel the need to punish yourself? Do you know what your triggers are?

Be well and know that you can work through this.