1 step forward, 10 steps back

Help: how do you cope with getting rejected from something you've worked super hard for? Everytime I'm finally happy something has to come and push me back down x10 more harder, I'm starting to become more and more isolated, I don't want to talk to anyone, my friends family. I don't want to seek advice from doctors but would rather do it behind a closed screen. I'm an optimistic person, well I once was, now with everything's that happening; family problems, dealing with witnessing a close family death, exams, university application stress, rejection and bullying ... I was never one to be in that position, I was always the bubbly girl who knew everyone and I guess was "popular" but now, I feel like everyone is talking about me, I feel like every starres and I can't cope with anything anymore, I've shut everything out and everytime I try to push myself up and do some charity work, or a new project I just get laughed at and pushed down... I don't know if I have depression as I've never spoken to anyone about this apart from you guys ... How do I cope with this feeling of rejection and failure... Sorry if this sounds desperate ... But I am, I seriously am starting to give up and I don't want to be that person, and I don't want to bring a bad name upon my family