I had exactly the same thing however my DS tongue tie wasn't found and snipped till 12 weeks! Whilst there was a noticeable change in feeding straight away it took a good few weeks till he was feeding well still not perfect but a lot less painful now!
I am on the same tablets for my milk supply and once he was able to feed better my supply picked up, again still not perfect but better. I have never been able to express much at all even using the hospital grade pumps.
Also try nipple shields I know they are not liked by many but they let everything heal so quickly, I wouldn't have been able to continue with out them.