solids for a 4 month old.

Went for our daughters 4th month checkup today. Doctor told us we can start on solids. I thought solids started at 6 months but she said doctors now want to start early in case of food allergies. I know this is my doctor but I'm just a little worried because I do feed her formula and breast milk. When I shared my concerns with the doctor she said I can feed my daughter solids for breastfeed lunch and dinner and either give her breastmilk or formula inbetween feedings as a snack. She also said I can start giving her water. So my question for you all is, when did your baby start solids? Did you continue to feed her breastmilk/formula?