You might be able to tough this out. You’ve already demonstrated that you have enormous inner strength. But why would you want to go it alone? This sounds like a terribly lonely and sad way to live. Your friend is probably right. You can get through this much more quickly, if you have the support of your parents and the practical help a therapist can give to you. Seeking help isn’t “resorting” to anything. It is often the mature way to handle an unfamiliar and serious problem. You tried to do it on your own. To your credit, you got better for awhile. But since you were only talking to yourself, you didn’t get the benefit of learning some new ways to cope and to manage your feelings when you feel you are spiraling out of control.
I do think your first stop should be with your pediatrician. You are at an age where your body is going through enormous changes. It’s possible that hormonal shifts are a contributing factor to what you are experiencing. You at least want to rule that out.
I wish you well.