Not cheating

Why does my bf always think I'm cheating but he won't say it. He will just FaceTime me then say "who's there?"  I say no one and he will tell me to move the camera around the room. It's happened about six or seven times in the last couple of months. I tell him the same thing each time. That I'm not interested in anyone; I'm not interested in cheating on him; I love him like I've never loved anyone and I'm sick of him hinting around like someone would be at our place here.  We live in Vegas, but I'm working out of state at the moment and we have a place here as well as Vegas.  He goes back and worth and will be with me 7-10 days then back to Vegas. It's when I'm here and he's there that we have a problem. I really irritates me that he thinks I'd cheat on him. Seriously I'm too damn old and tired to be cheating on him. I go to work and come home and chill and do it all over again the next day. Today when he asked me "who's that?"  I ask him what? He says "you looked over to the side". Really?  I can't look anywhere but at the phone now?  I've told him numerous times that it's an insult to me when he is essentially accusing me of cheating. Oh and today he asks me "what's that on your neck?"  I don't get it. I've never done anything to make him suspicious of me and really I don't think he's cheating either so WHYYYYYY????
I'm 98% confident he's not cheating. We also share our locations Indefinitely so at any time I can pull up where he (his phone) is.