i breast fed for 2 weeks after dd was born in december, and it was agonising and not filling her up at all despite her feeding literally for hours. and yes, she was definitely feeding. she would easily drain both breasts in a sitting
i would have switched to bottle feeding sooner but you're right, the pressure to breast feed is huge. in fact, when i was in the ward after giving birth, the doctor stood in the middle and gave us all a lecture on why we should be breast feeding
i suffered huge guilt, but i just couldn't get on with it - sore boobs, cracked nipples, baby crying non stop with hunger (ALL day long on christmas day!), plus i had to go and sit alone for hours to do it, which meant i was effectively the only one spending any waking time with our new baby
now i have a contented, fully fed baby and i'm glad i switched - despite knowing all the advantages of breast feeding. if i hadn't i'd be losing the plot by now
it's worth giving it a go just for the convenience if nothing else, but at the end of the day it's your choice. having a baby's about much more than how you feed it