Feeling like I'm fighting a loosing battle

Baby number 4. Born at 38 weeks is now 2 weeks old. I really set myself to breastfeed. My oldest I did maybe a month. My middle only lasted a week due to jaundice and poor knowledge. My youngest was like 3 weeks and turned out he was lactose intolerant so I gave up. Now youngest is two weeks and I want to throw in the towel so bad. My boyfriend (this is his first) is rly pushing for me to breastfeed(because formula is so expensive) but I'm really struggling here. The bag will eat for a hour straight sleep for 20 minutes and then be up and want to eat again. I feed and then my boob is empty switch then that ones empty. I literally can't do anything I'm always feeding this baby. I feel like she's not eating enough but she did gain weight. We left the hospital the 31st she was 6p11oz(born the 29th 7p4oz) and on the 8th she was 7p2oz. Since Friday she's had 2oz of formula every day due to her jaundice. I feel so lost and like I'm fighting a loosing battle here.