Hey nickel,
I got nosebleeds in my first trimester and am getting them now too - you're right - our mucus membranes are very thin and all that extra blood doesn't help either - I will just start gushing for no apparent reason - always seems to happen around small children - had to reassure my class of 5 year olds that I was fine and also the other day (with blood all over my shirt!) my eight year old that this is completely normal and I'm not in pain.
I don't go anywhere without those little packs of tissues now.