A.R.
You should see a lactation consultant with the initials IBCLC after her name. In the meantime, try to attend a La Leche League meeting and see if the leader can see the problem. Sometimes viewing the nursing from different angle (not mommy's angle!) can shed light on the problem.
It sounds like a tongue-tie or tongue thrust to me. My second daughter had a tongue thrust and she would put her tongue out to suck and it made it incredibly painful, but with the help of an LC and a lot of patience latching and re-latching, we finally got it right (and she is still nursing at almost 3 years old. Yay!)
Lansinoh can make it worse if you are allergic to wool, by the way.
Try undressing the both of you for some skin-to-skin contact first. Babies nurse better that way since they are more relaxed. Don't wait to nurse until he is STARVING, and just sit in a comfy spot with a big glass of water and snack for you, any pillows, etc and tell yourself you are going to "practice" for half an hour, an hour, etc. and try to get him in a position that isn't painful.
I would do all of the steps you see online where there are great photos of how to nurse in the correct positions (or any books you have.) This won't replace an LC's advice, which is totally invaluable!! but it might help you in the meantime. Do those things you think you "know" how to do already, like making sure the mouth is wide open and tongue is down, bringing the baby to YOU instead of leaning in toward the baby, trying a football hold, pointing the chin at the nipple when you bring him in to nurse, etc. If you last nursed a toddler, you could be expecting too much too. That was one of my problems- I wasn't guiding the baby like I should have been.
If he still latches on hurts and you don't think it's a tongue issue, try this:
Let him latch and then, with your finger, go around his entire mouth and gently rub his lips outward so they are very pooched out around your nipple- it could be that he is sucking in some of his lip too and causing friction. Usually it is the bottom lip that causes and issue, but some babies do both/either. It won't give you a PERFECT latch, but it may help make it more comfy.
Latch, latch, and re-latch different ways, trying different things. And pay the $100 or so for an certified LC. I know a great one named Peggy Healy, if you want to Google her. She is amazing and will travel to your home and weigh the baby before and after nursing, etc.
Hope this helps!
M.