How do I deal with an abusive terminal patient?

My boyfriend is terminal with head and neck cancer, given 6 months or less. He is emotionally, verbally and a few times physically abusive. He only does this to me. Hes got 2 daughters that are blind to the situation and wont move in. He says hes fine and they dont have a clue. He's becoming a danger to himself as well. Forgetting things, losing things, spending money constantly on crazy things. He doesnt eat properly at all or follow drs directions with his meds. Hes all over the place like a child with adhd. He argues about everything and insists things have happened which havent. He says hes not afraid to die but i assume this is part of the problem. He doesnt want me to do things for him anymore. He has a g tube and doesnt eat his special liquid diet as hes supposed to. I dont know where to turn. Im the only one that sees this. If i tell the dr, he will really go crazy and even if the dr prescibed something, he wouldnt take it. Other than saying goodbye to the man i love, is there help out there? Im only a girlfriend. We're not married. I dont have rights. I feel like im dying. The stress of it all is killing me