Thumper the humper , who knew ?

EWww. my rabbit wich i love with all my heart . Tryed to hump me O_o I was WTH GET OFF ME!! (screem ) He is old about 5 years. HE was about everything yesterday he humped my webkinz , his litter box ect.. Why is he me and my friends ? Why is he litter boxes and stuff ? how do i get him to stop trying to hump me and my freinds o_O ok just for da record , I stil love him but im just really grossed out and have to be careful when im tanning outiside in my bikini and stuff :(