Yep. Gained 15 lbs when I weaned my second. I was underweight while Being DD2, so 5 lbs would have been okay, but that 10 was not hot.
It took me a very long time to lose those 10 lbs, I will be honest. I had to count calories, take a hard look at my diet and habits, and really cut alcohol. That helped, but I had some injuries that I needed to deal with before I could start really working out again. Once I was able to start running again, the rest of the weight slowly came off.
My youngest is now 5 and I am in great shape. But it took five years...