Is this signs of a lactose intolerance

3👼🌈💖2018🌈💙2020💖2021💙2023 • God's timing is perfect🙏⛪

This is my one month olds diaper it looks brown but it's not it's yellow he is mostly breastfed would maybe a half an ounce to an ounce of formula every once in awhile he has been having tummy issues and me and his doctor are trying to figure it out