baby feed for only 5 mins on 1 side !

My baby 4.5m. Her routine is, wake up feed for about 5 mins on 1 side and let go, I would try to burp her and feed again but she scream and push me away so I try to feed her again before she sleep which is in about another 45-1hr. She doesn't complete her feeding as she dont empty my breast at each feeding. I used to bottle feed her a week ago whenever she was very fussy or I needed some time off but now only DL & stopped it as I thought she might prefer bottle but it still stays the same. I even started taking fenugreek to increase my supply which I think is working too. It's sometimes very sad when she rejects my breast and makes me cry in frustration. I get less rest and work done because I have to keep feeding her throughout her wake time so she gets full milk. Her weight is only 5.5kg for 4.5m she should be 6kg and above. How can I make her finish her feeding and be full for 2-3 hours and gain more weight ?