20 and life is already falling apart!?

i was with my gf 4 3yrs in which she was my first love stood by me throw everything!***** of asked 4 a beta person 2 fall in love with,we split last week mday i think if was by the tuesday nyt she was sleeping with sum1 else nd is stil with her!has she eva truly loved me?now i am scread i myt hurt myself as i cant deal with watching her love sum1 else,i have to pick my mams sleeping tablets up 2mz witch they are 28 temazapan 20mg each i am scread i wil take them all to end the pain of loseing the most special person i had in my life plz help me!if the worsed happend nd i tuk them wud i die or just go in2 a coma?