How to gain milk supply back after formula

Kat
For a few days I gave my baby formula. Now my milk supply is almost gone and I regret it... I used to make 5 ounces each boob but now I can only make 1 ounce out of each boob. I'm pumping every 3 hours and breast feeding now. She has to take formula while I'm at work cause I don't make enough. I'm drinking mothers milk tea. Not working too well... What do I do???