Fourth day breastfeeding! So desperate, nipples hurt so bad.

My baby is 4 days old and I feel so clueless to what im doing. When I got discharge they told me to feed her when she gets hungry or every 3 hrs. They told me to look out for signs (smacking lips, being fussy, etc) they taught me a few positions to bf and I have bf so much. I do switch sides but she starts crying when I think she's "done eating" when I give her the breast she starts sucking again. Yesterday was really bad and seeing her cry made me.nervous so I would quickly have her latch on except I might have been doing it wrong because it hurted. Today I can't imagine to bf because I feel sore and they hurt so bad. not sure what to do. Would it be okay if I formula fed her today til tomorrow? I have an appointment tomorrow which I will also be talking a breastfeeding consultant to see what I'm doing wrong and how I can ease the pain. I just don't want to give her formula if its bad?? Sorry I'm a ftm and nervous, I don't want it upsetting her stomach or making her sick.