Is a pinch of rice cereal ok to put in my 3 week olds formula?

Not unless doc says: Putting rice cereal in infant's formula is not a good idea. If you are just trying to satisfy for a longer interval between feeds because they want to eat so often, it's a really bad idea. They are signaling to you they need more formula and calories, not filling them up with their systems are not designed to handle. If they are refluxing baby, doc may suggest it, but only under close supervision.