Hi K., How sore are you, on a scale of 1 to 10? 1 being sore just after initial latch, 10 being unbearably sore for duration of feeding.
Have you sought the advice of a lactation consultant? I did with 2 out of 3 of my children and they were amazing!!! My problems disappeared after following their advice. I don't know where you live, but Maternal Expressions in Folsom, CA runs a consulting service as part of their business. Look them up and they should be able to refer you to a certified lactation consultant near you.
If you have already seen a lactation consultant, then you need to see one again asap. Jack has clearly become fond of his latching method. Somehow it sounds like he is being rewarded but his mommy is being tortured!!! My heart goes out to you because I remember how terribly painful the beginning stages of breastfeeding can be. DON'T GIVE UP HOPE! You and Jack can and will overcome this temporary problem. Best wishes to you. Regards, A.