Part of the problem is having flat nipples, which LO will eventually reshape. I had those too, and it's *not* easy.
I wasn't aware that pus in the nipple was a mastitis symptom, but glad you're being followed closely
Some latching problems are just due to LO's mouth being small--it's a mechanical problem. LO will get bigger and grow into a better latch. Ouch, the truth hurts, doesn't it?

It took 6 weeks for my pain to appreciably reduce, and then around 8 wks I realized it didn't hurt anymore. YMMV--I also have Reynaud's phenomenon which caused vasospasms and was bfing in the dead of winter, which exacerbated the situation. However, I am so very very glad that I stuck with it, minute by minute sometimes. It's far easier to bf than use artificial milk, and the best way to stop a toddler tantrum in its tracks. I'm so happy we perservered because bfing for me has been my #1 mothering tool

and with a toddler, plus pg, I need all of them that I can get!