It sounds very likely that you're retaining water due to weight lifting. However, that's a GOOD thing. For about 1-2 days after lifting your body needs to repair the muscles that your tore during lifting and during that time you're actually burning extra calories!
So, yes, it's very realistic that the weight lifting caused you some water retention but that weight WILL go away so keep up the good work!!! I know it can be discouraging to see a higher number on the scale but know that it's only temporary and if you keep up with your diet and exercise the scale will continue to go down (I've lost almost 35lbs since I started lifting
).
Now, it could also be your cycle. Are you ovulating? Is your period coming? There are a lot of things can cause unexpected weight gain. I actually weigh daily and from that I can see some fairly clear trends. The day after lifting (or, well, any exercise for that matter) I'm up at least 1-2lbs. Also when ovulating or TOM is here I increase some pounds. Additionally, if we ate out recently or I've had more junk food than usual I weight more temporarily.
Just know that it's normal and keep up the good work!!!!