I have G breasts and am currently feeding dd (4.5mo) perfectly fine!
I too had the incredibly sore nipples for about a month but that was due to poor attachment as she just wasnt opening her mouth wide enough. Once we both worked out what we needed to do (pull down chin and shove boob in) then in a few days the pain just went away.
What you are feeling has NOTHING to do with big boobs.
I feed dd with a pillow under her and she is kinda tucked under my boob across my tummy if that makes sense.
It will get easier....I promise!