If you are in a relationship, you are bound to the agreement you made with that person. They were there first. This means if someone else wants to date you and shows interest and you are not sure if you want to really dissolve your current relationship or if you are just wanting to be with the new person, there is a solution.
It is an equation of evaluation. So you need to evaluate based on the rule that you don’t cheat and that the partner was their first. This means you only break up with them if you would want to break up with them even if the other person was not known at all. If you would keep your partner if the other person was not around, it means you should work on the relationship and not do anything with the other relationship possibility.