I went through a similar faze for the first few months of my engagement. Not arguing so much, more having an internal battle about whether this was the right thing to do if he really is "the one” that type of thing. For me it passed and it was because I asked someone else for help.
I told them I knew I loved him it was just that I had this worry that it wouldn’t last because what if there is someone out there in the world that is more perfect for me or him and we meet them later in life etc. When I get married I hope it is forever. This person replied to me "I will know when it is the right person when I cannot imagine my life without them". For me that is true and all my worries fell away.
Perhaps you have a specific worry that is making you act this way and once you have addressed that it will stop?
I don’t know if that made sense or if it was any help, but there you go x x