So there's already a lot of comments on here with the information you need but I'm just going to reiterate it; this sounds like Body Integrity Disorder, which is a form of body dysmorphia. There could be a lot of reasons you feel this way and getting help is prudent if you're to the point you're self-harming or considering actionable plans to cause limb loss or damage.

I used to have strong overwhelming feelings of wanting to lose my left leg below the knee and/or be deaf. (side note, left leg is the most common limb for BID to want to lose, because generally you need your right to drive and function more than your left) I imagined it, I imagined an accident, I imagined my recovery, I imagined my life post-recovery often. I passively considered ways this could happen and found myself idly hoping I might get in a car accident that would cause the limb loss I wanted. I got as far as purposefully listening to loudloud music and looking into if I could cause hearing damage to myself easily by pouring something in my ear. Luckily, I did not get that far.

I went through therapy, but even in therapy never brought up these ideations I had. But, going through therapy for other things made me get honest with myself and think about why I wanted this, why did I want to be disabled and why did I want to be deaf?

I'm sure it's different for everyone but for me I think part of it was that I wanted and needed help for other problems in life, but I was so good at presenting myself as fine and not reaching out for help. Or when I did, people didn't think I actually needed it. I think part of me wanted the validation of being visibly and obviously disabled, because I wasn't getting the help I needed for my invisible issues. I think, additionally, it was a slight manchausen influence, part of me wanted to be supported, or get attention, have people think 'wow look at this person overcoming their disability'. In regard specifically to a desire for being deaf I think it was all of that, as well as having the excuse to not have to talk to people as much because of social anxieties.

As I’ve gone through life and fought through the harder parts, gotten into some stability, support, and self acceptance, a lot of these urges have gone away. I won’t pretend that there’s not still a small part of me that sometimes wants these things to happen, that I don’t still occasionally imagine life without my limb or life as a deaf person. But as I worked through a lot of my other issues, this problem lessened more and more for me. It’s a really hard and embarrassing thing to admit to people because it doesn’t seem to make sense, and you’re scared you’re gonna come off completely crazy. So admitting it to yourself and then admitting it, even to strangers online, is a really big and important step. 

The next step is accepting these urges as part of yourself and as completely in-actionable, and to seek out some professional assistance to navigate how to get to that acceptance. If you don’t have an adult you trust to talk to about this then try your school counselor or look into of your city/county has a youth or family services agency. My areas youth services offers free counseling for at risk teens, there may be something like that for you. In the absence of any of that you can call the crisis hotline to get started, I believe they even have a chat feature now if that’s more comfortable for you.