When im about to start sex i get a little nervous and i shiver a little. I've had sex a few times and all with the same partner but i always get a little nervous and i cant seem to grow out of it. Also sometimes im so nervous that when were doing it my penis goes a little soft and it never seems to go fully erect, it also happens when im getting a favor, but when im giving a favor my penis is fully erect in my pants. Im 15, i know im young but still, please help?