not looking for a pity party

E
I don't want to sound whiny bc I know there are plenty of moms who had to go back to work immediately after having their baby, but I worked 30 hours a week when he turned 3 months and just switched to 40 hours this week. He's 7 months now. I had a feeling I would have a hard time with the first day or two, but now I'm on day 4 and I still feel like there's an elephant on my chest. I suffer from GAD, so it's normal for me to have anxiety.. I just don't think I've had it this bad, this consistently, ever. It's only another 10 hours a week. I don't understand why it's beating me up so much.