We all are just human, and no one has a crystal ball up their sleeve, which could tell us 100% that our relationship is THE ONE. So, of course, some doubts or questions about the relationship are perfectly normal. Yes, even for long-time couples.
That being said, don’t let doubts define your behavior in the relationship. Figure out what to do when you have relationship doubts, and work on them before they start negatively impacting your relationship.