What to do after five years in a relationship?

I have been in a relationship with the same man for five years. We have stayed together on and off during that time. We now have been steadily living together for almost two months. We have been thru pretty much all of the ups and downs of a relationship. Every time I try to discuss taking our relationship further he starts an argument with me about it. That is literally the only thing we don't discuss and we really don't argue about anything EXCEPT when that discussion comes up. Our relationship is a long story, but to make it short he has made a lot of empty promises to me and we have worked thru all of the problems with that up until now. I have forgiven him for the many things he has done to hurt me. Now my thing is, he promised we would get married THIS YEAR. And even though I love him more than anything (and i've made this clear to him) if he doesn't follow thru with that promise, I feel like I need to move on with my life. He does a lot to keep stringing me along, like every once in a while he'll ask me what names I like for kids, he even went as far as taking me to look at rings. He knows this is all I want but it supposedly scares him. He basically makes it a joke with everyone.And we have discussions when we are around our friends and of course each side is biased, the guys say its too much to handle and the girls say its as good now as any other time. So i have a few questions to ask about the subject: Why does he stay with me knowing he doesn't want the same things? How do I start the "getting more serious discussion" without starting an argument? How do we come to a compromise on the subjects of getting married and starting a family?