Talking about honesty briefly would be fairly normal.... a long drawn out discussion that occurs repeatedly would make me think the person was either insecure or cheating....
You have to relax and TRUST your partner. There are no guarantees that a person will not leave or cheat on you. All you can do is be the best person you can be, try to keep the relationship stable and healthy, and hope that will be enough.
You cannot control the other person nor request guarantees of their fidelity.
"The weakest soul, knowing its own weakness, and believing this truth that strength can only be developed by effort and practice, will, thus believing, at once begin to exert itself, and, adding effort to effort, patience to patience, and strength to strength, will never cease to develop, and will at last grow divinely strong."
- James Allen