J.
Hi A.,
Congratulations on your new baby boy. I think the pain may be caused by a bad latch. Have you contacted the La Leche League? The leaders are more knowledgeable about breastfeeding then doctors & pediatricians. And the best thing is it's free! Here's the link: http://www.lalecheleague.org/leaderinfo.html
Here's a link that describes a good latch:
http://www.kellymom.com/newman/a-when_latching.html
As far as cutting out the formula, keep nursing as much as possible. Adding more nursing sessions is the best way to increase your supply.
J.