Your weight alone is not a clear indicator of how much body fat you've lost.
When strength training you will also produce more dense muscle mass, which is heavy.
It is quite likely that you have lost body fat, increase lean muscle which has increased your over-all weight. In the mirror though, you will look slimmer and more defined.
To measure properly, you'll need to keep track of the size of your waist, arms, and thighs.
J