I gained 50lbs in pregnancy and then lost 25lbs within the first two weeks or so.
With DS #1, I gained 39 lbs. I think when I came home from the hospital, I lost 12 lbs. Another 18 lbs. came off within 2 weeks, then the last stubborn 10 lbs. took a few months more.
With DS #2, I started out 10 lbs. heavier than I did before DS #1, but this time I only gained 33 lbs. Oddly, when I came home from the hospital, I only lost 4 lbs. (after having a 8lb11oz kid, LOL!) I was down 20 lbs. or so within the first month, and once again I had to fight to get the last 10 lbs off. At 3 1/2 months PP now, I'm 2 lbs away from my pre-preggo weight, but what counts to me is being able to wear all my pre-preggo pants, which I've been doing for over a month now.
I was a little overweight to begin with and I gained 35lbs during my PGcy. I highly recommended not going all out in terms of food and try to get some exercise daily. I tried to watch what I ate but if I was craving something, I went for it. I also walked nearly everyday but that is largely due to the fact that I take public transit to work and have to walk to/from the bus and train.
Within 2 weeks PP, I lost 25 of the 35lbs just from BFing. I've been struggling to lose the last 10 (and then some) because BFing causes me to be hungry all the time! I just weighed myself this morning and I'm down another 5lbs so still got the last 5 of the baby weight to go. I think I fit into my pre-pgcy clothes after 1 month but not comfortably. I had to go out and buy some fat pants but now those are big on me. I also had to buy a lot of new tops as most of my old ones are now too tight in the bust.
Like the others said, don't stress about it too much, esp. if you'll be BFing. I don't push myself to workout right now but I do try to watch what I eat.