I’m truly sorry life seems so difficult. I’m sure you have reasons for concluding that you are are unattractive or that you are not worth other people’s time. I don’t have enough information to understand what has happened to you that has resulted in such a low self-esteem. But I do know that you are incorrect. Everyone is attractive in their own way. Everyone has important things to contribute to the world. Part of coming into our own is to find meaning in life — and to find other people to like and love who like and love us back. I’m not saying it is easy. Often, it isn’t. But the result is worth the effort.
I do have enough information to see that you already know that you need some help. Trust those instincts!
The first stop should be with your doctor. Sometimes the shifting of moods in a person your age is due to a medical issue like hormone levels being off, a vitamin deficiency or a sleep disorder. Make sure you are physically fine before you decide your problems are psychological.
If you are medically okay, make the next step. Find a therapist in your area who specializes in teens. If you could have solved your problems on your own, you would have done so long ago. I do understand that talking anonymously to us seems safer. But we just don’t have enough information to sort things out long term. A therapist will give you kind and attentive support while you deal with your confusions.
In the meantime, I encourage you to join one of the forums on PsychCentral. People from all over the world who have similar issues talk to each other and support each other.
I wish you well.