Help!

Wanting to know if anyone here had problems with baby latching the first few weeks? My daughter hadn't gained any weight at her 2 week check up so doc told me to give her expressed milk but said I can still breast feed and bottle feed. So if this happened to you did you successfully breastfeed after you got baby to latch? Im pumping but it's not more than 2-3 oz at a time and im waiting to see a lactation consultant. My freezer supply from previous baby is about to run out though and I'm freaking out!!!