Well, what do you mean by nursing constantly? My DS did what felt like nursing constantly too and it was just the way he is, he likes a lot of contact and really liked to nurse. He is tongue tied so that meant that he would get tired nursing, take a long time, and wake up needing to nurse all over again. My day and night looked like this: nurse for 45min-1hr 15min (ish) then he would sleep and nurse again at two hour intervals....from the beginning of one feeding to the next which was only a 45 min break. Then on top of that, he would cluster feed from 6-9pm where he pretty much nursed that whole time. DD is different in that she will nurse quickly, no tongue tie, but she nurses often. The doctor recommended small frequent feedings for her due to reflux and I just laughed because she can nurse up to 10 times in a 2hr period. DS nursed that frequently until after a year old, but he got much quicker. DD seems to get frantic if she just wants to suck and my milk keeps coming down...but she gets mad if I stop nursing her. What I am trying to say is that at least for my kids, it has been the way they solve everything, hunger, overstimulation, tiredness, fear, loneliness, etc= nurse. When they get older it is more easy to distinguish but right now, DD uses it to normalize and reorient herself a lot. If she isn't being worn, she is usually nursing. She definitely falls into the category of needing that "fourth trimester" approach. It is hard. I hope you get answers that help. It sounds like you have worked really hard to give your LO all that she needs. It sounds too like she is gaining well. I hope you can get off the shields soon, you have had to have a lot of extras in your nursing with her, you will think it is a piece of cake when you can just pop her on the boob and not have to worry about everything else!
oh and to add something else, not sure where to put it, but as far as working out etc ( from the other thread), I would totally wait and just deal with the stress of figuring out feeding a newborn before I tried to tackle weight. Just my two cents worth, figuring out feeding is stressful enough if you are running into challenges.