I feel like a terrible mother…

I have two kids (currently pregnant with my third). With my first I feel like I’m more lenient (but also he’s a really good kid). My second oh man does she ever challenge me!!! She frustrates the ****outta me! She’s into everything. She’s constantly screaming and crying. She never wants to go to bed. Everything’s a challenge with that one.

I feel bad but like I get way more upset/angry with her when she does something, rather than if my son did something. They’re both very young (under 4). How can I fix this? Her personality just challenges me and triggers me when she acts certain ways. I obviously love her. But it really bothers me . I don’t want her growing up thinking that I don’t love her or I love her siblings more than her .

Is this normal? Is there something wrong with me?