Would it be a bad idea?

So my baby is 3 weeks old & I breastfeed & bottle feed(breast milk). I went from making 4oz w both to 2 oz. I’m exhausted & once I start to pump it feels like nothing wants to come out anymore. Almost to the point where I can only make a few bottles a day. Would it be wrong to switching her to formula Today & feeding her at least a bottle of breast milk a day while I freeze whatever else I have?