Yes, I formula fed my baby up until 6 months. However a bit different than you, when my sister had a baby in April, she strictly pumps, and always gets a lot of milk so started giving me some of it for my daughter. I haven't seen any problems since I started feeding her both, I'm sure it's even better than strictly feeding formula because breast milk has all the good stuff formula doesn't.
Let's Glow!
Achieve your health goals from period to parenting.