Breastfeeding problem/question someone pls help

Hi ladies, well my LO is a 1month nd 2weeks old . She was born weighing 4pounds, I breastfeed nd her dr told me I had to add formula after each feeding to make her gain weight. Now that she's 7 pounds her dr told me it was ok to breast feed her only .
The problem comes here, she used to get milk wasted nd now she doesn't . My breast just seem saggy with like no milk supply if I'm lucky I get 3ounces when I pump but usually it's an ounce each breast.
I really really want to breast feed her only but my mom keeps saying I'm not making enough to fill her up nd tries to make me give her formula at all times . I mean I'm not sure if she's getting enough, she latches on good nd stays on for like 20 -25 minutes and falls asleep.
There's time when she gets frustrated and thats when I know my milk supply is really low .
What can I do? How do I know she's getting enough and how can I increase my milk supply to take away formula completely?
*first time being a mom  

as long as shes gaining weight you should be fine if you want to increase your milk pump everytime after feeding her and drink mothers milk tea

Don't worry just keep at it! Is your baby crying after a feeding or acting satisfied? If your supply feels low or your baby is getting fussy during a feeding my nicu nurse told me to pump for 10 minutes after each feeding to boost supply. Also just letting her nurse on demand as long as she wants will help boost your supply. You likely are making enough. If you want you can get a baby scale strip her down before a feeding and weigh her. Then feed her and weigh her again. That is going to be the best way to figure out how much she's getting. You can try skin to skin and mothers milk tea too.

Cut out all formula, nurse around the clock. Make sure you're drinking enough water and eating enough calories (500 more than your normal diet is good- so if you normally eat 2000, now eat 2500). To check to see if she's getting enough, look for wet diapers. Don't worry about dirty diapers though, just wet. Is she nursing or are you bottle feeding?

just keep putting her to the boob! If she is having enough wet diapers she is good.

Quoting lifeslovely:" Hi ladies, well my LO is a 1month nd 2weeks old . She was born weighing 4pounds, I breastfeed nd her ... [snip!] ... I know she's getting enough and how can I increase my milk supply to take away formula completely? *first time being a mom  "

You wont know if she is getting enough until she gains weight in about 22 weeks. Some women's breasts will adjust to the increased demand and some wont.
Give it your best shot and be ready to accept whatever the outcome is.
Her health is most important and should be celebrated. If you cannot BF her 100%, dont beat yourself up about it as that is the way it is sometimes.

There r herbs to help like fenugreek and mothers milk tea. if u google lactation herbs u should get a long list. When ur changing how much baby drinks ur milk supply has ti catch up. Im going thru the same thing since we r changing schedules. Keep at it pump also and dont let anyone discourage u. Nurse more often and thatll help ur supply as well as get lo the nutrition needed.