He lied again!!! Need advice

My SO and i made a promise if either of us ended up doing drugs tell the other and also lets just not fucking do them. And he has broken this promise twice now and both times i didnt find out from him. I found out from everyone else but him and i dont see why i should keep trying in a relationship that he cant respect me by keeping a promise. Also the day after he did them he lied straight to my face about doing drugs and was like i dont do them cuz i love u. Should i even bother giving him another chance?? i am sersiously done cuz he keeps disrespecting me and not giving me the same amount of effort i give him.