What has happened to me? please check my question its really important..?

These days i m feeling like a loser.. feeling like i don't win anything..i'm feeling very very depressed, feeling alone.. feeling like i've lost my concentration power..this problem arised after my maths paper.. i first time got really bad marks.. and i cried for 2 days.. omg it was such a horrible experience..my parents were mad at me.. and i was like a perinnial river..i lost all my confidence..and now even if i knw the answer i don't knw what happens to me i just do that wrong.. during viva etc i just don't knw what happens the teacher asks me a ques.. nd i'm like a statue.. even though i knw the answer i'm unable to answer it.. i rarely have any friend.. i just hope u all can help me a bit build my confidence back..i'll be really thankful to u..