bekki
i found some information on the nct website which you may find helpful. it's some dos and donts for supporting women who are bf - here .
perhaps you could show this to members of your family before the event, a bit less confrontational?
there are also links to the facts and figure of why breast is best - so they may be interested in those too.
if your dh is on-side, maybe he could be the one to do the confrontations, if you are too shy? e.g. tell members of the family to keep their opinions to themselves - in the most diplomatic way possible of course, at least at first.
otherwise, perhaps you could ask members of your family to leave the room themselves if they have a problem or just say "it's like footie, if you don't want to know the score, look away now..."
in terms of support for yourself, i can recommend the nct bf helpline (number in the link above). they are very helpful and may even be able to get a local bf counsellor to come and visit you and give advice.
i also recommend a book called Bestfeeding . It's a little bit hokey but has loads of pictures so you can check the latch and positioning easily.
hth - and i really hope things are better for you next time.
ps - if you prefer some peace and quiet when your bf or your baby is easily distracted, then imo, there's nothing wrong with retreating to the bedroom or feeding room, but you shouldn't be forced into it by the ignorant attitude of others.