Good for you, Tea!!!
I tend to do that also, gain about a pound after exercise. I noticed it the other week when I decided to check my weight after my nightly workout before going to bed. I was like what the heck!?!?! Then I realized what was happening because the next morning that pound plus some was gone.
I juggle my workouts once in the early day and again at night because with 3 children, I just don't have time to sit on a bike for an hour and then the treadmill for 40 more minutes. Add to that the strength training and I would have to hire a babysitter, haha. I decided to check it after my morning workout several days ago and it doesn't happen then, only during the nightly workout.
Like I said earlier; our bodies can do some
very strange things for whatever reason.
At least now you know when you move up in weights to possibly expect this.
I know everyone says not to dwell on it and move forward, but I know it must have been frustrating when you know you did everything right. And aparently you did!