Formula to Milk

So my doctor told me I could start slowly introducing whole milk to my daughter since she’s almost a year old and she will be done with formula soon! I’m a FTM but it seems the past two days I’ve gave her just maybe 3 or 4 Oz of whole milk Through the day and at night she’s getting gas/upset tummy! I know that I will be talking to her doctor for sure but until then I wanted some help from you kind mommies! Do you think she could be lactose intolerant or is this how babies adjust ??? Did anyone end up not being able to give their baby whole milk ?? What did you do instead??