Hey Sara

You are doing a GREAT job - this breastfeeding stuff sure is challenging and something that takes time and patience (as I've found out!). You will get there, just keep persisting and if it doesn't feel right, then it probably isn't right. That's what I've learnt.
If it hurts, try to change her position, even if you have to take her off and attach again. All the girls have given great advice.
Keep that LC close by to you like I have done with mine. It's the BEST thing I could have done was hire an LC... money well spent! I was just about ready to give up BFing 2 weeks ago but with the help of the LC I have come along way with Ava.

As you know (from my BF thread) I've had so many problems with BFing, attachment issues, low supply due to Ava not sucking effectively, painful cracked sore nipples to the point I couldn't breastfeed anymore from it and took 5 days to heal it and only just today am I using it again

I have to hold my boobs too as they are so big, it does make it difficult but it will get easier.... soon you'll be a pro It's only now, for me, after 4 weeks that I'm only JUST getting the hang of it!!! And yes, I too felt like I wasn't able to enjoy BFing too because it was so painful every time she attached, I would cry and get so tense and stressed it was awful....

eta - with nipple shields it's best to only use them under the advice of an LC as they "can" effect your milk supply I believe. I don't use mine. Yet others use them and don't have problems.

As for how long they feed, try to follow your baby's lead. Watch her face as she feeds. If she looks like she's ready for a burp and starts to kinda pull off a little bit perhaps bring her off gently and give her a burp then offer the other side if she was on for long enough on the first side. Again, check with your LC she will tell you what's best for you and your situation... I agree it sure does feel like all we ever do is sit on the couch or lie on the bed and feed!!!
Lying down position can be good for sore nipples i found.