How many times is baby eating ?

My son just turned four months and we had his checkup, Doctor said everything looked okay. She asked how often he's eating and I said about every 3-4 hours. Sometimes he snacks in between, he's breastfed only. Doctor said that was okay. Now my friend is with her four month old and her doctor told her eating every 1-2 hours is normal (for breastfed baby). So now I'm worried! Is my baby eating enough ? If I feed him every 2 hours he spits up a lot.