Yeah...screaming baby. Oof. Been there. He was still doing it up to 9 hours a day until about 2 years old. It switched from belly trouble to angry toddler with barely a breath in between. He's one stubborn fella'. Sometimes I wonder if his pain as an infant made him have a short fuse...or if his pain wasn't as bad as it seemed and he just had a short fuse anyway. Who knows. But, what I DO know is that I am really, really, really enjoying him now. He is the sweetest little guy.
And, you've got firsthand experience. You know that this stage isn't THEM, and it isn't YOU. You love them (though you might not like them right now), and they love you. In fact, you adore each other. It did help me a lot, like a pp said, to think of the baby's pain. I look back and tell myself over and over that ds was technically sick. He was not a "normal" baby, and we did not have a "normal" experience.
But, you know what? We did a lot of growing, and the whole experience made him who he is and who we are today. I certainly wish I had acted with a lot more grace, but I recognize that I lived just below my absolute breaking point and in a state of exhaustion for nearly 2 years. I'm actually kind of proud of that.
If you've done this more than once, you should know you are an awesome Mama. All mamas make sacrifices for their children, but a screaming baby is TOUGH. You had another baby, gave another person life KNOWING that it could be this way again. You did all the hard work, and you are still giving because of this spring of love in you.
You may not look it, and you may not feel it right now, but you need to hold in front of yourself that you are a GOOD mama.

You CAN do this.