My baby is 10 days old. I make enough breastmilk but only every like 4-6 hours and she needs to eat every hour and a half - 2 hours so in between she will have formula. Or if I’m passed out and my husband has her he will feed her formula all night instead of waking me up . Is this okay for her and her stomach ? She also like the formula better but I still want her to be having some breastmilk