Need Advice! Sore nipples from BF

Sarah • Baby girl was due 2/2 but made her appearance on 1/17 💖
I just had my baby girl 13 days ago and I am breastfeeding but it has become harder and harder to because my nipples are so incredibly sore! It feel like someone is sticking pins and needles into them every time I breastfeed. She's very small born at only 5lb 9oz so her mouth is very tiny so I'm finding it hard to get enough of my nipple into her mouth, I'm thinking that's the cause of the pain but I can't do anything about it because it's not like I can make her mouth bigger. I'm using nipple cream after pumping and breastfeeding but it's still excruciating to breastfeed her. My SO bought me a nipple guard which I do use now and it does help a bit with the pain but I don't want to have to use it all the time because I heard it can decrease your milk supply. Does anyone have any advice? I don't want to stop breastfeeding. I'm so desperate