T.B.
First of all, we need to know how old your baby is. Secondly, milk doesn't just disappear overnight. Even when a breastfeeding mother weans her child, her breasts will produce milk for weeks afterwards, sometimes up to a year. Thirdly, you cannot gauge how much milk you produce by how much milk you pump. How a baby sucks at the breast is far superior pumping than a breast pump. You indicate that your baby is frustrated at the breast. We need to establish why: (1) how old is he, (2) is he teething (3) have you introduced solids.
Added:
Okay, I see you updated some info. Is he gaining weight? How many wet/soiled diapers is he producing? Teething is a huge factor! If you give a baby a bottle, the contents of the bottle will continuously drip out so this is what happens: put bottle in baby's mouth, milk drips out, causes baby to swallow, and baby continues to swallow as milk drips out. There really is no "work" in drinking from a bottle. Baby just swallows. Easy breezy. Now, on the breast, baby wants milk, he has to suck. Is he sucking? Do you see him swallowing? My baby is going to be 12 months old in a few days. She just got 4 teeth all at once. Poor baby is miserable and cranky and sometimes she just wants to suckle, not nurse. The best I can offer is that you contact a certified lactation consultant. I can mostly promise that your milk doesn't just dry up overnight. Just because you may not feel a let down, just because baby is acting frustrated, and just because you pump a couple of ounces~ these are not indicators that your milk is gone. Sometimes babies go on a nursing strike. My first born went on a strike when she was about 12 months old. It sends a new mommy into a crazy, "oh my goodness, what should I do" paranoid state of mind. Just keep offering your breasts and it also helps if you are able to lie down in a quiet darkened room with your baby. A 9 mth old gets quite distracted and that could also be a valid reason. Don't give up and don't rely on the bottle either because I can tell you that the more you offer the bottle, the less milk you make and the less milk you make, well, you know what happens. It's a downward spiral. Keep pumping regularly, stay hydrated, and try to not stress about it.
There could be many reasons why the baby is frustrated. Maybe he's not hungry. Wait a while. He could be teething and uncomfortable.
To truly understand what is going on, we really need more info. My advice to you is to call your local hospital and ask if there are any certified lactation consultants on staff. If not, contact your pediatrician and ask if they know of any certified lactation consultants. If all else fails, look for LLL (La Leche League) in your area to help you locate a consultant who is certified.