I experienced sore nipples only during the first 2 few days. Lactaction consultant advised correct deep latching, i.e. baby's mouth should cover the whole nipple aerola. I suggest you to seek lactaction consultant's help as soon as possible to check on correct latching techniques. Meanwhile, you can check out youtube videos on how to latch correctly. For example, https://youtu.be/7FJuBn2bgNk
Do try other latching position which make yourself more comfortable while latching. I like side lying position the most.