. I don't know what to do about my relationship, do I walk away for good or stay and try and make it work

We have been dating for 2 years now. I have grown to love him more and more as time passes. He has a lot of health issues and not a very long life expectancy like we all normally would have. But that doesn't matter to me. We have been on and then off for a week and sometimes up to a few months at a time. He claims he loves me so much and wants to get married but I don't understand why he continues to do this. There have been times that I will not answer a call or even return texts but he constantly will not leave me alone. He got angry with me about telling his cousin the truth about an issues and called me to tell me to leave his family alone and to stop talking to them. What have I don't for him to be so ugly? He has done this plenty before and expects me to take him back and act like everything is ok. Mind you that he does this with his family as well. Every time we get back together the relationship is better than the previous time. Maybe it is over this time and he won't be calling wanting to get back together but how will I know if I am doing right by walking away? Will I regret it? I don't know what to do, half of me wants to walk away and the other half doesn't cuz I do love him. And the relationship may not be the same cuz his family and I will have tension. This time I refuse to answer or return any texts, just not gonna do it. His sister came to stay with him for a while and I knew she was going to cause problems for us. So this would be hard to deal with. Up until this drama his family loved me and appreciated me but now I don't know what they think. Can anyone help me.