I can't stop yelling at my 5 year old please help

I have a very wilfull 5 year old boy and a 15 month old babygirl. My son only listens when he feels like it, he's such a sweet boy but my god does he like to push my buttons. I know it's wrong for me to yell and it hurts me so much that I do but I can't stop yelling at him no matter how hard I try to.Like I said he only listens when he wants, I have tried rewarding good behavior, taking toys/phone/tablet away, not giving him candy but nothing seems to work. He will listen after I take away whatever I told him I would and hes good but within an hour again he is not following rules. He only listens if I yell.For example I will tell him finish your food or you don't get candy, he will halfway finish, say he's full, eat his piece of candy then sneaks away some more candy when I'm not looking and eat it all after I told him only one piece. I will tell him to stop doing something and he will keep doing it over and over and over until I finally get frustrated and yell at him to stop and he does, only after I yell. He knows what is ok to do and what is not ok, he knows the consequences, he knows when he does something me or his dad won't be happy about but still does it.If I tell him to put the phone away while eating he will cry and say he will eat, and proceeds to play on the phone and let his food get cold, then I go take the phone away and he will cry and say ok ok I will listen and doesn't let me take it away and tells me to leave it next to him and that he won't touch it, and I let him because at least that way he will actually eat then if I take it away he will only cry way more, not eat, and end up just getting up finding the phone and putting it next to him.He is very smart as far as school, always getting 100 percent on tests and doing hard things in class with ease, he just wants to do what he wants when he wants. I feel terrible for yelling, it's not healthy and I'm sure it will affect him, both me and my husband get stressed out by him, we both find ourselves yelling at him, and telling each other to stop yelling but we continue to do so.His grandma and his aunt used to babysit him but they both said they couldn't anymore because he would stress them out by not listening. I work full time, I go pick him after work from school, then go pick up the baby, and still have to shower them, cook dinner, clean, take myself a shower, it's like I never get a break, my husband helps but not much, even if he tried my kids will only fall asleep faster and do everything if I'm the one to do it with them.He's always been like this, I just have no patience, I get frustrated easily, I get stressed, I don't know what to do, I feel like a horrible mom, I cry at night because I feel bad for yelling at him, I even curse more than I'd like to admit, I'm just so tired. Other than that I love my kids, they are my world my everything, I would do anything for them, I say I would never let anyone hurt them, but ironically I'm the one hurting them by yelling :( via /r/Parenting http://ift.tt/2nNeF5R