Falling in love; unrequited love; being loved by someone who doesn't appeal; etc, etc, etc, ~ they are all part of growing and maturing.
Yes, it can cause great elation and happiness, or great upset and sadness, but, if you are feeling, or ever do feel, suicidal, then that is a completely different matter.
Suicidal feelings and depression can be triggered by upsetting events, but they, in themselves, are symptoms of illness, and they require medical attention.
If you feel this way, then you should talk to someone who can help you. Schools, churches and medical centres often have ~ or have access to ~ counsellors and psychologists. There are even free help lines that you can phone.
Everyone goes through rough times. There are other people on here ~ young and older ~ who have had either personal or family experience of such difficulties and also experience of professional help. Help and support are available, if you feel really down. Do not forget that. There is usually light at the end of any tunnel
In this case, it would really be better for you to stop dwelling on this girl and to find other interests. You can't help how you feel about her, but you can throw yourself into other activities ~ activities which do not include watching her or day-dreaming about her. They are not doing you any good.
Why are you doing all the work, while others are having fun?
I am guessing that this is because you are choosing this path.
Find another path.
Join a club, where fellow members share your hobbies, for example.
Can you talk to your parents about this? ~ A problem shared is a problem halved.
If not, find a counsellor to talk to; one you can trust.
I think that it might help.
One day, you will find your Miss Right and you will be her Mr Right. It will happen, so try not to worry ~ and start enjoying your youth.