You've done so well already . I'm a working mum as well and my milk supply also drops recently, I'm also trying to pump more frequently to increase my milk supply. May be you can try to pump both side at the same time. or pump while you are feeding your baby. It works for me
I don't know why you baby does not like to be fed, but I recall, when I'm frustrated, my baby also knows. Therefore, may be you can try to turn music on and sing to your baby when you are feeding. It may relax both you and your baby and make it a more enjoyable time for you two.