Hey, All I could think about when you said that you've been so severely unhappy for all these years is how unbelievably difficult that must have been to struggle through this alone for so long. No one should have to do that. You have every right in the world to be completely frustrated and upset right now. It's definitely time to do something to try to turn this around. You're absolutely right that you can only put up with this for so long.
To start, I think it's pretty clear that you are severely unhappy. Not just "kind of down" or "having a bad day". That is a major sign of clinical depression, especially when coupled with the constant thoughts of suicide you're having. While it is possible to get past depression without the help of a doctor, it can be extremely difficult. Above anything else, I really want to recommend that you try talking to someone about this and hopefully get some medical attention (or are at least screened for depression). If you are covered by your parents insurance, this will probably involve talking to them about what you're going through.
I completely understand that talking to a parent about emotional stuff can be really awkward and uncomfortable. I know for me when I was in high school and dealing with a lot of stuff, I didn't want to tell my mom because I didn't want her to think that I couldn't take care of things on my own, and I didn't want her to worry about it. In the long run though, your parents really do care about you (you said it yourself...) and they would most likely do anything to help you get through this. Will that initial conversation when you admit to what you've been feeling be uncomfortable? Yeah, probably. But trust me, it gets a lot easier after you get everything out into the open. You start to realize that you're parents are human beings too, and that they understand you aren't perfect. They really want what's best for you. All you have to do is let them help you. I cannot stress enough how worth it is to let them.
If you absolutely cannot talk to your parents for whatever reason, I urge you to seek out a friend you can confide in. You said that you have a really close friend, but you really don't talk about things. I just want to point out that just because you haven't ever talked about this before doesn't mean you're not allowed to now. Friends are supposed to be there for you in times like this. They are a fantastic resource for whenever you really just need someone to talk to, vent, or just let everything out. It might seem like it's not worth the risk or trouble, but I think that in the long run having a friend that's going to be there for you through this could really help a lot. These negative feelings you're having aren't just going to go away overnight, even if you get some treatment for it, and having someone who knows what's going on could make it a little easier.
If none of these are options, you may want to consider taking some time to talk to a school counselor. You wouldn't have to tell your friends or parents about it at all, and you would have no obligation to receive any treatment. However it could really help you to take some of this off your shoulders by just talking to someone in a confidential and professional atmosphere. I know meeting up with a stranger to do this is intimidating, but counselors are really just normal people who want to help people in your situation. It's definitely worth a shot, at least.
Again, you are dealing with a tremendous amount of pretty negative feelings here. You've been feeling like this for a really long time, and I think it's time for a change. You absolutely aren't a "wuss" for not hurting yourself yet. In fact, I'd say it's the exact opposite. It takes a lot out of a person to fight so long through all this, and you've managed to do it for four years. That takes a pretty strong person, in my opinion. However, it's time to let someone else help you fight this. You can't do this alone forever. There are so many better, happier sides to life that you're missing out on by shutting everyone out.
Obviously, no one can force you to do anything here. All I can do is strongly urge you to reach out for help. Your life and happiness are worth it. You deserve so much more out of life than what you've been experiencing for the last few years, but it's up to you to take that first step and reach out. You can help get yourself out of this.
I really wish the best for you. If you want to talk to someone at all, or have any questions, feel free to PM me. I would be happy to help.
Take care.
-Isobel