HELP SOOO CONFUSING!!!!!!!! HOW DO U KNO IF HE IS GONG TO HURT YOU?

why do most guys love to hurt girl and not even CARE. ive had this 1 guy he BROKE UP WITH ME THROUGH A TEXT MESSAGE ON VALIENTINES DAY FOR ONE OF HIS EXS AND DONT CARE WAT SO EVER!!! plz how do you know if he is going to hurt you:(