How much does placenta and fluid weigh?

I'm getting quite down about my weight at moment, joined slimming world 3 weeks ago, not had to change too much about how i eat. I can only do green days as i'm veggie but i'm weighing out pasta etc and cooking with fry lite not oil so adjusted where needed and stuck to it religously, i lost a bloody pound, couldn't believe it. So pi**ed off, went and bought a galaxy as it doesn't seem to make any difference. i googled baby weight and fluid question and most replies from others asking was you lose about 20 lb in all what with the birth and pushing etc. I don't know what i weighed at start of last pregnancy so can't compare but was quite pleased with the thought of coming out of hospital 20 lb lighter leaving myself about 2 stone to lose. However went to midwife today and asked her on top of say an 8lb baby what other weight could i expect to come off and she said about 3 lb. Thats very depressing. Also my OH said i can't expect to lose weight this late in pregnancy so don't expect miracles from slimming world yet but others who done it pregnant have lost quit a bit, what also pi**es me off is i'm walking and jogging on treadmill about 3 times a week and stay quite active but nothing is shifting, whats going on? has anyone else had experiences like this?
sorry for rant
kerry, frankie 16months and boy bump 39 wks xxx