Insecurities ruining my relationship

Hi, I've been dating my best friend of five years for almost a year now. I've always been the size I am now; short and a little chubby. Anyways, he's been working this new job that has very stupid hours and keeps him away usually six days a week. He works with two really pretty blondes along with an attractive brunette manager. Everyday I go to drop him off one of the blondes has to yell across the parking lot to him. Other days when he's getting off, she makes flirtatious winks saying he's not allowed to leave. He doesn't show any interest in them while I'm there of course, but while I'm home or work, I don't know and it worries me. It really bothers me, but every time I bring up any insecurities I have to him, he gets upset because he doesn't see why I feel the way I do because he's never been a cheating type or one to break hearts. I just would really like to know how to deal with this in an adult manner. I love him and trust him, but I don't feel the same for the ladies he works with. I hope that makes sense. Thanks in advance for any advice.