Intimacy 🙊

So , me and my partner have a little problem his the only one I’ve ever let touch me in a sexual way .. and well every time we try to do it I just can’t leave my legs open ( I hope this makes sense 🤦🏻‍♀️) we’ve tried missionary to start with and also doggie but every-time his about to put it in and I feel the pressure I don’t know my legs freak or something and they shut down on me and close and I kinda get embarrass that I can’t do it ... idk what to do Can someone help me I feel like this is not natural lol