Why does he hate me so much ?

My boyfriend and myself were together for like 2 months, and he was like i love u and really clingy.. so i eventually dumped him.. now he really hates me.. and is vile to me .. saying how much he wants to kill me.. and wen we went out he was digging a hole saying this is your grave.. i dont get what i have to to make him hate me so much! GEEZ help ? :/