Is it okay?

It’s totally ok. Different parents have different way to deal with parenting and that includes feeding. If feeding fm to your baby relieves some of your stress and allow you to be able to take care of your kid better, why not? Ultimately, a happy parent will result in a happy baby. Fm is not poison. I myself had fed fm to my twins though I am able to produce enough fm for them. I was so stressed out, having to pump milk often while hearing them crying out for me. I had help but still I felt overwhelmed taking care of them while pumping that I decided to feed fm. I was able to handle them much better after that and I was able to manage my emotion a lot easier which result in calming the babies a lot faster. So do what you can to survive the first few years and try to ignore the advices given by outsiders. It’s always easy to say than do.