I wanna go campin but my mom wont let me what should i do?

sorry so long... so im 18, and have been goin out wit my bf, whos 19, for 3 years. we have been together for all 3 years with no breaks and have never broken up. we do act like kids some times but knw wen we need to be serious. i think we are very responsible i dont drink, smoke, or do ne drugs, he used to drink very lil n smoke very very lil but he respected me not doin ne of that so he doesnt do it ne more. my problem is that his whole family, mom dad brothers sister uncles aunts everyone, have a campin trip n theyr leavin today. his family invited me. its only gonna be till sunday and my mom refuses to let me go. were gonna be wit his whole family jet skiing swimmin jus havin fun. she says that we need to stop playin house. she claims thatwere goin jus cuz were gonna sleep together but were gonna stay in a tent wit his brothers n his couzins were all around the same age. but shes constantly tellin us things and has always been the main thing that me n my bf fight about. i always tell her wen im leavin, where im goin, if plans change i tell her. if i wanna go somewher i always ask her wether if its to the store or to a game everywhere. so i think im very truthworthy and honest. i knw shes my mom n she has my health n my safety always in mind but i feel that she really jus likes tellin me no wen i really really want something. i really dont think that its fair to me or him. how can i get her to let me go and to trust me or what should i do?