Being comfortable in your own skin is key. Nothing anyone says can make you feel confident. You have to know that when you go in there and get naked for a shoot, you have to own it and make it yours! Ask questions, so you know what is being expected of you!
Look in the mirror beforehand, in the nude, and appreciate your flaws! Tell the mirror “ I’m sexy I’m beautiful and I’m confident. “ and you must believe what you are saying! It may seem cliche but these exercises work! Have fun and don’t worry about your insecurities!