My boyfriend and best friend

Ok so I got grounded and I haven’t been able to talk to my boyfriend or any of my friends on the phone. Well, my boyfriend and best friend are friends and my best friend,(we’ll call her sue), talks to him more than I talk to him. They will talk on the phone from 3:00 in the afternoon after school until 2:00 in the morning. NON-STOP! I don’t even talk to him that much. I talk to him off and on for maybe a total of 3 hours. And that’s off and on. Sue and,(we’ll call him Harry), talk all the time. Well I asked Sue one day if she will take me to Harry’s house for a couple of hours and she said no. Because he lives in (we’ll call it Bongville). Well I just found out by two other friends that she is going to his house this weekend in Bongville. So I have a question. What do you think is going on between them? I mean they will sit there and text back and forth and neither one of them will tell me what they are talking about. He will tell her stuff and he won’t even tell me. She’ll stay the night with me and when I’m on the phone with him, he will barely talk, but when he gets ont he phone with Sue, it’s like he won’t shutup. He’ll just keep talking and talking. And when I want to talk to him again he’ll say well I got to go cause I’m tired. Or when he gets off the phone with me saying he’s tired. He’ll call Sue and talk to her for another 4 to 8 hours. So again, what do you think is going on between them? Do you think he is cheating on me with my best friend?!