I'm an H cup and found a good nursing pillow made a ton of difference, that, and a good nursing chair.
Make sure it has good back support and quite high arm rests - the cheapest one from IKEA works pretty well, but it has to be the cheapest one because it has slightly higher arm rests than the more expensive ones and you sit lower down so you don't need a foot rest.
Looks something like this:
http://media.tumblr.com/tumblr_ldrhp4ilEM1qehao3.jpgWhen I got the nursing pillow it was like a 'eureka' moment though:) Mine is pretty firm so that LO doesn't sink and mess up the latch.
You have to try all the holds to find one that suits you. For us cradle works best, rugby is ok, reclining is weird but I have never been able to get side laying because I have to make sure I'm holding my breast with one hand all the time and I need to be higher than DD is, otherwise my breast totally covers poor LOs nose and laying down it's just too tempting to fall asleep.
I guess every one is different and you have to wiggle around a bit to find something comfortable, it took me about a month to feel semi-comfortable with one position.
Basically I have her on the pillow and the pillow pretty high up and close in so I have both hands free and can hold my breast with the one and control flying hands with the other;)
My friend has normal sized breasts and I was so jealous to see her BF while walking around because her LO just latched on, she held her with one arm and the other was free to cook! No way I could ever do that.
Make sure you also have a really good nursing bra, it has to have pretty thick material to give you enough support. The only 2 companies that I am happy with are Cake Lingerie and HotMilk. Unfortunately both are really expensive but the cheaper bras just have very thin material and were sooo uncomfortable because those breasts get HEAVY.
I also had massive oversupply till about 5mo! It go so bad that I couldn't leave the house because I was leaking constantly and crying in pain:/
How long did you block feed for? For me it took about 3-4 days of block feeding to see any kind of a difference (and I know that with other on the forum it took up to a week). Cold cabbage leaves in your bra are also fantastic, they take the pain away. I think I spent a week smelling of cabbage because I even slept in them and had a pair on the bed side table to change when I woke up at night.
I think after the first time my oversupply got out of hand I quickly learnt how to identify the symptoms and could nip it in the bud with block feeding and cabbage, before it got out of hand again.
Anyway, what I'm trying to say is that if you are prepared, then it can be done so don't panic:))