why do i feel so lonely & empty?

Hello!

So I (17/f) have had suicidal thoughts and cutted myself when i was 15/16. I don't know why i had those thoughts or why i was so sad and felt the urge to hurt myself. i was always unaware of what caused this behaviour, because i did have some problems with my family/friends, but i think those problmes were normal for my age. I never went to a therapist and not a single soul knew about all those things.

anyway, i got better in the last 1 1/2 years, i felt happy to be alive and i was afraid to die again. I also gained self esteem in that phase (i WAS literally the most insecure person i know) plus i stopped cutting myslef.

sounds good, but in the last months I'm struggling; I just feel so lonely because every single person in my enviroment just knows the half of me. I'm still extremely introverted and my self esteem seems to be in retrograde... I do go out with friends, I have my clique at school... yet still i feel unwanted and i can't handle the slightest rejection. Lately, i feel the urge to go home and be alone when I'm with my friends. I know this is a contradictory, but i don't think the people i consider as my friend are my 'real friends'. i mean i can laugh with them and talk with them about everything but i think i would regret telling them my past.

At the same time, i feel empty, because there's nothing i live for.

What is wrong with me? I can't remeber anything in my past that could have caused depression.