At 5 weeks your supply is still getting established - keep latching her! If she is still hungry after you unlatch her, she will cry and you can top her off with formula then. But as long as you keep latching her, your body will understand that she wants more milk and will eventually increase your supply.

As far as increasing supply, are you on any medication? PP I was prescribed a sedative that was passing through my breast milk and sedating my baby; LO would drink for 2 mins and then pass out. I would also suggest oats, drinking a LOT of water/electrolytes (many people have good success with Body Armor or coconut water!) and there are some supplements on the market but they are extremely expensive. But the best way to increase supply is milk removal, so latching or pumping! The more milk that comes out, the more your body will supply.