If your baby is gaining weight, it is getting enough milk. I had a problem with a low milk and used a Supplemental Nursing System. Mendela makes one. The system allows you to give the baby both breast milk and formula at the same time. It also prevents nipple confusion which happens when bottles are introduced. Lactation consultants are helpful to meet with, as well.
Pumping is not a true indicator of a low supply. baby is more efficient and will get way more than a pump. What she is doing sounds very normal, bf babies eat more often because breast milk digests quicker. The fact that she falls asleep without fussing or rooting makes it sound like she is satisfied. A good indicator of a low supply is not enough wet and dirty diapers, if she is having plebty then she is getting enough. I would not supplement if you really would like to bf because it will hurt your supply more
How old is your baby? It's recommended to not use a pump at all within the 1st month because it will make the baby lazier about latching, if there's a nipple readily available on a bottle that's easy to get to, and it decreases your milk supply. I went between pumping and BF'ing at about 2 weeks and woke up one morning and my milk was completely gone! The best way to increase your milk supply is getting the baby to latch more often, and switch between breasts after 15-20 minutes of feeding, if she's falling asleep try to take her onsie off so she's stimulated, and awake, in a bright room, and doesn't fall asleep quickly.
i do have her latch also but she only drinks for about 10 mins then lets go, goes to sleep and wakes up about 30 mins later to eat again....is that normal?
If you don't think you are producing enough keep your baby latched as much as possible. Your baby's sucking helps tell your body how much you need so much better than a pump.