In shambles

I was changing my baby’s shirt because it’s pretty warm in the house and were suppose to go out and I didn’t want her ruining her shirt with slob. I take her shirt off & she falls forward trying to grab her feet and I quickly grab her and she starts screaming to the top of her lungs. Instantly filled with confusion because I don’t know why she’s screaming but she’s screaming like I’ve never heard before & in 6 months I’ve heard so many screams but nothing like this. I figured I had scratched her but I’m still confused because I don’t know where I would’ve done it so I’m searching where I grabbed her and I see a long scratch on her shoulder (no bleeding & it has gone away) and for the first time I couldnt calm her down and bust out crying. I give her so many kisses and she calms down about 3 minutes later. I call my S/O & of course he reassures me and she’s perfectly fine but I can’t keep it together. I have so much mommy guilt (I think I’m using it right). My nails are super thick & a decent length due to my prenatals, will be cutting them as soon as I put her down for a nap. I’m assuming my emotions hit me harder due to me being pregnant but 20 mins later & im still a wreck. Being a first time mom & making mistakes is just the worst.