My fiance calls me too much

So, I love him dearly. He has a tendency to call me way too much though. He calls me when I'm busy and expects me to be able to talk but I can't, and I think he gets disappointed and when he does call me and I answer I think I seem a little bit short because he asks me if I'm okay. And I've tried to tell him that I'm busy but he still will call me and then call again if I don't answer the first time. Any advice on what I can say to him that won't make me come across as mean? I really do love him and he treats me well, he just calls me way too much and at the wrong times. I don't want to be glued to my phone 24/7. And it's not like we don't see each other, we spend every weekend together and FaceTime at night.