What should i Do..Best Guy Friend Is totally two faced?

My best friend thats a guy is so two faced... i honestly don't know what to do... It bother me because we are so tight even if i want to stop beinghis friend i can't because i care abotu him to much .. I stopped him from suiside a year ago aas well.. He will talk **** or say all these stuff aout someone behind their back and then to their face hes like their best fried like today he was invited to a girls birthday and behind her back he wa s like i hate her shes so flat and shes so annoying so never shuts up and all this and now hes going o her party like wtf? Then when he asks why im mad im scared to tell him like i am actually scared of what he'll say and.. if i do tell him then he says all this really really sweet stuff to make me never want to stop being friends with him. Like the other day i told him i was done with him and he said this.."Don't say your done... Don't give up.. I want to be able to talk to someone about things that bother me.I want to be with you britney so dont"be done with me" Please<3" Everyone says we like eachother but i promise we don't... What should i doo!?!?!