Can't stand my kids

Ok il start off by saying I love my kids very much. I have a 3 year old and a 1 year old. It literally like everything I say and do they will not listen. Ill also say that this whole time I have been a parent I have not gotten a break from them or to just do something for myself unless it's to go to the store or something small like that. Im just over being with them all the time. I try to not lose my shit bit its every day this happens. I try time out, sitting on the couch or chair, taking my 3 year olds tablet away and yes I do smack his butt. Nothing seems to work. I tell my 1 year old to stop doing something and my 3 year old starts doing it so now they both won't listen to me. I feel like a horrible mom cuz all I seem to do is yell. I realize that's not good but I am at my wots end I don't know what to do. I don't think my 1 year old would be so bad if my 3 year old would listen. Its like he just totally ignores everything and continues what you tell him not to. Ots hard to explain really but ill take pointers if anyone has any