3 weeks 4 days still struggling to breastfeed 😭😭😭😭😭😭 help!! I want to give up but I can’t!

Love

Ladies, I really need help. I going nuts!! Everyday I want to give up breastfeeding but then we have a good feeding and I change my mind. I cry almost everyday from the struggle. Baby hasn’t gain weight only a few oz. I give her formula through a syringe when I feel she hasn’t eaten well. But I guess she’s never eating well based on her weight gain. Last night I gave her a bottle after a feeding and she’s been fighting me more during feeds. The doctor has us going back for weight follow ups once or twice a week. He says to feed her every 4 hours and to let her drain me. The first LC I saw said to let her eat 20min on each breast every 2.5-3 hrs and the one we are currently working with said to hand express 10 min and to let her feed 30-40 min max an hr per breast so 10 of expressing and the rest on breast. The ped said this was to long and she will get tired. I don’t know who’s rule to follow. She cries, gets mad and won’t latch. Because I’m so worried about her weight everytime she cries I think it’s because she’s hungry and she won’t latch and I cry with her and then I think well maybe she’s not hungry. But what if she is. I am want that bond with her but it’s seriously making crazy and maybe depressed. I’m obsessed with this and I can’t think of anything else. I wish I could just let it got and decide to pump and give her a bottle but I can’t. I have a breastfeeding support class in a couple of days and I think that will be my final straw to decide if I should just give up. I’m not sure if my supply is low and I think it is because she’s not gaining weight so I started taking liquid gold from legendary milk. I need advise please, before I got anymore nuts. Why is this so difficult? Why can other moms succeed and I can’t?? How long did it take you to become a pro at breastfeeding? I feel bipolar one min I want to breastfeed and the next I want to give up. Help 😭😭😭😭😭