What formula?

I’ve been breastfeeding for a week now, I love the bond it gives me and my daughter and we’ve both been doing great until yesterday my nipples are so so sore now everytime she latches it hurts so bad like stings. I put nipple cream on I thought her latch was good but it’s starting to not be so good she doesn’t open her mouth all the way. Anyways I feel like a failure once again but I think it’d be best to switch her over to formula my nipples can’t handle it anymore :( what’s a good formula to try out first?