Decided to post a longer answer here instead of in the comment section:
To the question asker, yes it is possible. Attachment issues have a lot to do with trust. People with attachment issues don't really trust anyone. Even if they say they do, they won't act like it. The problem with it is, he has to want to get over it. Until he does, he just wants "casual" cause it makes him feel comfortable. Pushing him into anything will push him away. Freedom is more important than love to people that have trust problems. Even if they don't say it, it's how they act.
You need to understand the things you will do to try to help him get over his issues are the very things that push him away. In your mind you are going to think if you show him how loving and trustworthy you are, he will stay. But showing him that will build intimacy in him, that is the feeling he pulls away from. It's like this. The man I love, we had the most intimate, the most loving sex I have ever had in my life one night and the very first thought I had when it was over was "We need to break up." I didn't even know why I felt that way. I just did. I was uncomfortable with the closeness of the situation. I didn't break up with him cause it woke me up to how bad my attachment issues are. But any traditional thing you can do isn't going to work probably cause he is going to misread it as you needing him too much.
All I can say is let him be. He needs to decide on his own if he wants more. People who don't push us and don't need us are the ones we like the best.
To Wolfie, I have seen several people like this, not just a couple boyfriends. Myself included. Some people do develop attachments and some don't. The way you do it, speaking from personal experience, is not being impulsive. It's choosing not to call up the person you want to out of the blue. Cause you finally realize you will stop talking to them again in 3 days. It's getting with the person you love and waiting out the bad days. You will pace like a caged wolf sometimes. There will be really bad days where you want to just throw up your hands and go "OK I'm out!" But you literally have to just push throw those days cause the next day you will probably not want to leave as much. I wish I could say it's just changing your mindset but it isn't. It's a day to day thing that I have been doing for years now with the same man and I still want to jump ship half the days. What makes it easier is finding someone who doesn't push and doesn't chase. I like that your name is wolfie cause I think people with this issue are like wolves. They aren't dogs that you just love and accept you cause they are just naturally that way. They are like wolves that stay with you cause they want to. You never really own one. If you can find a girl that says "Ok I'll let you come back when you ready." It will make you want to stay with her. Cause you'll stop thinking others are too needy and it will let you realize that you want them.