21 month old and 3 week old... DRAINED

I feel like the worst mom ever. The first 2 weeks with my newborn were pretty easy, of course. Once we hit week 3, it was up and down. She will be a month old on Saturday and the past 2 days have been absolutely dreadful, if she’s awake, she’s screaming. This was the case before as well but she slept a ton, so we never really saw her awake. The past couple days, she’s been refusing to sleep for most of the day, which results in her screaming her head off. This results in me losing my patience with her and my toddler. My poor son is getting the battered mommy because I just don’t have the energy to handle him after dealing with her constant screaming. I’m hoping that this screaming phase will come to an end soon because I am so worn out. I finally broke today and just cried and cried. Please, someone at least relate and make me feel a little better. I miss my sleepy little girl who was so cooperative.