My boyfriend thinks i lied about my body count

Serenity • west indian , 19
he called me at 11:40 knowing his birthday was the next day , he yelled and cursed at me and more calling me a liar and etc. asking who i have been f*ing and sucking , he is being really shady towards me. 
and honestly i think its because of my jealous no good cousin who always cant mind her business what so ever like, from screen shotting my snaps and more sending them to her little group chats . WHY MUST SHE WORRY ABOUT WHAT IM DOING . 
 will it br wrong to beat her ass lol?