Any ideas of why she'd be scratching?

Ever since my baby has been able to sit up on her own(5 months old) she has started scratching one side of her body (her right) if she is in the bath or sitting in a onesie without pants on. I'm at a loss of why she does this, I figured I'd give it time to see if it was just her figuring out how to use her fingers. It's been a couple months, she's 7.5 months old, and it hasn't changed at all. My hubs and I decided tonight after her bath that it can't be normal. I've decided I'll call her Ped on Monday, but I was hoping someone could give me some ideas of why she might be doing this. There are no signs of a rash, bumps, dry skin, redness (until after she itches the area), or anything that would make us think she's itchy. She itches it so hard that sometimes she breaks skin. It makes me so sad. 😢

These are things I have decided are NOT the problem:

-bath soap (we've tried 3 different types now, no change in the scratching)

-diaper (she's been in the same type since birth, so I assume it isn't the problem)

-diaper rash (she's never had it, and it's only on her sides that she scratches)

-food (she's been doing this scratching since before we started solids)

-breast milk (she's mostly BF and has been on the same formula almost since birth when I need to supplement)

-lotion (same as bath soap, we've tried 3 different types)

-detergent (we use dreft, we assume it isn't the problem since we've been using it since birth and the scratching is localized)

I hate thinking she's in any pain or discomfort. 😢 Any help would be great, thank you so much!