5mth old baby, sudden drop in supply.. quit pumping?

I hope some moms can help give me the support i need. my baby is 5 mths and ive been exclusively pumping since she was 5 days old because of her poor latch, i tried so so hard to make it work.. another issue that got brought in was when i started to pump my mom looked at the bottle and went 20ml only?! you HAVE to supplement with just a bit of formula! i wont let my grandchild starve! a whole damn week i ignored her and refused to supplement bcos i know there was nothing wrong with my supply in fact even the docs and nurses praised me and said i could pump way more than they got at the beginning! but a week later my mom jz fed my baby formula, i was too exhausted to argue and reason with her, so there began the supplementing that kept being a bitch problem to my supply ALL the friggin time! cos i was racing to pump every time the grandma or mother inlaw sneaked in a bottle of formula. i had mastitis twice, i have one flat nipple and my baby would only nurse on one side which is the flat one, just fine. The left side had always produced a lot less (based on measuring after pumping), im not sure why maybe its because i had minor surgery years ago in that breast.

When my baby hit the 3 month mark i really struggled with supply.. i felt like all i do is pump and pump.. its fine if i have supply but since last week i pumped as usual and i was surprised to get just tiny drops, i got at the most about 10-20ml for 40 minutes of pumping! I tried to let it go more than a week thinking maybe its just hormones and my period but still the same.. at the same time my baby shows signs that she wants to nurse BUT 9 out of 10 times she has a VERY shallow latch, i dont know how to accurately describe it but i think some moms have experienced this whereby baby sucks on and off, pull away then come back on then fall asleep, then you get up and they instantly look for you again cos they "seem" hungry still.. this whole routine is finally starting to really crush my patience and im thinking i should just quit but my question is if i slowly stop pumping, will i stop the production or will i end up getting clogged ducts that will lead to mastitis?

I guess another question i have is..should i quit? 😞 I'm going back to school in december.. I've been depressed about this problem for months and tried my best.. hope some moms can share some advise. thanks.