Sorry-wasn't sure what category to put this post in!!!!!

My milk output has been increasing as I am EBM feeding my 5 mo old and he is becoming increasingly hungry as he grows and I express to his hunger(I record what I express for my own reference). So he had this huge growth spurt or something as my milk output just shot up by about 6 oz or so overnight, literally and has been up for about 10 days or so. Thing is, I've gained almost 3 lbs in that time. My breasts also appear slightly bigger but I don't know which is a cause of which (if that makes any sense). I have been eating *less* than I usually do though and haven't made any other changes to my lifestyle so it doesn't make any sense. Does breast tissue grow as you make more milk, or is it all strictly fluid? Does a rise in your milk production make you gain weight? Please don't come on here and criticise me because it's only 3 lbs or w/e, I have been in remission (though not mentally) from anorexia for the past 2 years and struggling my rear off to keep it that way for the sake of my family.