Is this a phase for ~3.5 years old?

So my 3.5 year old has been deliberately not listening to me and I need to repeat myself so many times. Idk if it’s me failing at parenting or the fact that I have a baby due in a few weeks or if it’s just a normal phase. What does everyone think? Any suggestions, apart from yelling or flat out asking her why she’s not listening 😬🤦🏽‍♀️ I’m so tired of this and feeling so defeated