Perhaps as you stated.... He already senses that you are not sure if you love him anymore. That would make any guy insecure.
So my boyfriend keeps getting worried we will break up and I have told him countless times that we won't even though I don't know if i even love him anymore. He said he always pushes people away. I don't know what to do. Am I being selfish?
I think it's time you sit down with him and have this type of conversation:
"Bob, you and I have been dating for six months (fill in the appropriate time), and it seems like we are a good fit. However, you constantly asking me if we are going to break up is putting extra stress on this relationship that's not necessary.
You need to be secure enough in our relationship that you trust me and in turn, will lead me to trust you. Do you have any other indicators that we are going to break up, except your insecurities?
If not, then you need to drop the subject, because constantly asking if we are going to break up makes me want to break up with you. If you want this break up to happen, keep doing what you are doing.
I don't want you to keep asking if we are going to break up. I want you and I to date and be happy with that. If your feelings have changed, or if my feelings have changed, then we'll talk about that. But right now, you need to stop talking about breaking up."
See where this conversation leads you.