Is the milk to blame?

Ariella was exclusively breastfed until 6 months of age. We tried several formulas and soy was the only one that seemed to work for her. After reading a few terrible things about every day consumption of soy, I switched her to a lactose free formula. We recently started giving her whole milk and first started off with a lactose free. One day we ran out of it and had no choice but to give her the regular whole milk. She did fine for a week or two. Lately, she’s been very gassy and not sleeping nights. Her stool looks VERY light (pale yellow) and I was wondering if it’s the milk to blame or something else going on?