Wonky relationship

So I'm in this open relationship with a guy. He keeps saying he has feelings for me but its so on and off. The next second, he would say that we should keep it open and that he likes the openness of it. I like the openness too but I get so jealous sometimes. I told him that I get jealous though because we are very honest with our feelings and we talk about them often. I would like to be in a real relationship with him but he goes out and parties a lot and I feel like he would cheat on me if we became a couple. With his partying habits, I would just be too worried. I keep trying not to have feelings for him but its hard. My biggest fear is that he will find another girl he likes and he will leave me for her and I will be reduced to just a "friend". Anyone have any suggestions on how to control my feelings for him? Other than by ending this open relationship? Lol