Can’t burp baby

Me

My babygirl is 2 weeks old. She was born May 11th at 38 weeks. She’s a small baby, born at 6 pounds, went down to 5 pounds 9oz. She’s breastfed, occasionally bottle fed pumped milk. She spits up all the time, no matter what route she gets her milk. I think it may be because I can never get a burp out of her. I try over the shoulder, on my chest, over my legs. I usually alternate patting with rubbing her back with slight pressure. Nothing seems to work, any help appreciated.