S.R.
I have breastfed four babies for two years each and I can tell you I have my fair share of painful breast experiences!!
If your nipples are inflamed and red then it is thrush, you dont have to have been on antibiotics to get it, you could get it if your baby had a rash and you didnt wash your hands after changing the diaper, you could get it if someone who was dirty and didnt wash their hands held your baby or touched you and you breastfed right after.
if there are pink lines on your breast where the pain is, but no inflamed sore nipples, then its probably a breast infection and those are easier to cure (for me anyway)
for thrush, Gentian Violet worked in two days, i also ate yogurt and took acidopholus which is a vitamin you can find at any health food store.
for breast infection you want to take a a cold cabbage leaf and put it on your breast, then in the shower you want to soak your breast in hot (not too hot) water and expel the milk from the pained areas.
if it is neither, I would go to a gyno, since they are a specialist. if you can find a midwife they would probably do a better job of trying to help you. a doctor is just going to prescribe you meds so they get paid more.
ps i never took prescription meds for any of these and they went away faster with home remedies than the drs said they would with the meds! food for thought ;)