I’m a nanny and extremely frustrated all the time

So I nanny for a family and their kids are 7 and the other is almost 2. The 7 year old is at school for most of the day so it’s just me and the toddler. Recently I’ve been having a very hard time with him. He is purposely doing things ghat are wrong and he makes sure that I know he’s doing it. When I tell him no he laughs at me. I’ve felt so much hate towards him lately and I know that I shouldn’t. It’s just really hard when i try everything and nothing works. I feel absolutely terrible because most of the time I’m angry and not nice. Im also pregnant and it just makes me dread being a mom. But at the same time I’m so excitedly be a mom. I’m just so frustrated and I hope that this is normal to feel these things...