How do i not be shy around my boyfriend?

ok before i start this were both 13! its puppy love but here it goes im tired of being shy around him and i think its cause of this that im shy sometimes though i only see him when i go over to my friends house cause he is her cousent and sometime my friend says kiss kiss kiss we have kissed twice and its cause they dared us and i dont want every kiss to be like that and it makes me nervous and one time we were sledding and they asked me to sled down the hill and i said no cause i was nervouse i would fall or something but my boyfriend seems fine he is let loose but im not please help and im sorry if there was any misspellings!