I agree.
The more your baby demands milk, the more supply you will have. Each bottle of formula you give is telling your body to produce that much less milk.
During a growth spurt, your baby's demands increase, so they want to nurse all the time. This is great, because the more demand, the more supply. When you give formula, your breasts never notice the increased demand, so they don't increase their supply.
The best thing to do is just nurse, nurse, and then nurse some more! In a couple days, your supply will catch up to where it needs to be and things should settle down (until the next growth spurt!) Take a few days off, just lie in bed and nurse that baby!