Is my boyfriend suicidal or emotionally abusive..?

A couple days ago my boyfriend and I got into an argument. Not going to lie, it was heated & I was just as wrong as he was. However, he pulled out the box cutter that he uses for work & cut a very deep line across his arm. I was in shock at how calm he went about it & the emotionless stare I was getting while he did it. 
He told me it wouldn't happen again & later we both apologized for the argument.
Last night however, it got brought back up & lead to another argument. I told him that maybe we could use a day or so apart.
Not going into the whole argument but at one point he held the box cutter to his neck & said he would kill himself. In a panic I tried to grab it away from him, remembering what he had done to his arm, & when he jerked it back it ended up cutting me. 
He said it wasn't emotional abuse when I tried to talk to him about it bc he said he was serious & would have done it. 
He refuses to seek help & is very aggressive when I try to talk to him about it. 
I don't know what to do, nothing I do is right.. but I love him, I don't want to see him hurt or worse.. 
any advice to my insane situation is appreciated, I have no one to talk to about this & they would probably think I was crazy if I told them.