"How many times do I have to tell you that I love you?" One of the things we should examine is, "Why is this person asking over and over again do you love me?" There are several possible reasons.
Instead of letting your frustration burst out, think about what they are saying or at least what you think they are saying. They may be saying that, "If you really loved me you would be around more often and longer." They could also be saying, "I hear what you say to me, but I don't hear an adequate explanation why you can love me." Probably the first of these two explanations is the most important.
The reason is simple: time. Time and your use of it says a huge amount about who you are and what you value. People spend most of their time doing what they prefer to do. When they aren't spending time the way they want to, they usually complain loud and long. If you love someone and you don't choose to spend time with them, then they have a right to wonder about your real feelings."
There are other reasons of course, but we should pay careful attention to our use of time. We are saying things to our boss, friends, children spouse by our use of time, even when we think we've got it covered with words.
Keep in mind the question, "What am I communicating to myself and others?" It may aid you in the process of making a decision about what to do. Are you telling yourself that since you know why you're doing what you're doing your significant other will understand? Are you certain you know how they will interpret your nonverbals with the same interpretation you have?