Hi, first off, if you ever want to talk to anyone, you can send me a message. I've dealt with this first hand, so I know how you're feeling.
Also, it is a bad habit and I hope that you're considering quitting.
I know that it's hard, but I found it easier to quit when I had some support. My boyfriend and I both quit something together. My was obviously cutting, but his was something else, but either way it made it easier to stick to it.
Also, I think that your mom was wrong when she said that it's "stupid" and you have "no reason", but that it just my personal opinion. Have you ever talked to her or anyone about why you feel the need to cut?
Also, it's not stupid, but it is very dangerous. It's also a natural high, because it releases endorphins. So even if you don't have a specific reason, that could also be it. People argue this all the time, but I believe that cutting actually can be an addiction.
Anyway, like I said, if you want to talk, please, ask me.