If you were a distance runner, what you ate mattered - you were fueling higher carb for energy reserves to have something to burn. If you haven't changed anything in your diet, you may be finding that you're not consuming all of the carbs that you used to use for running. Further, if you weren't eating enough carbs, runners typically are more 'skinny fat' than lean - not that they are literally fat, but rather they have a lower proportion of lean muscle mass - - more specifically, running tends to consume all your readily available energy sources, and when your body runs out of that, it starts to go after the lean muscle mass as well. So again, if you're changing your body's fuel consumption, you are probably seeing it reflected in more lean muscle mass gained, less lean muscle mass being consumed for fuel, and as mentioned above, lean muscle weighs more than fat. So you're technically seeing a body recomposition, and not necessarily "getting fatter" w/ the change in weight.
If it makes you more comfortable (and the point of a successful 'lifestyle' - diet & training - is to do what you enjoy doing), you can add in more cardio to maybe find a happy medium between the running activity you did before & the lifting activity you do now. You can easily add some HIIT sessions or steady state - whatever you enjoy doing & doesn't aggravate any existing injuries.
I think the more important thing is to get to your goal - but your goals need to match up to what you are doing. Its not a bad thing that your weight is changing, as I mention above- your body is reflecting the change in your lifestyle. You might look at what you are eating, if you tend to consume a large proportion of carbs. Otherwise, don't feel like you need to make big changes to force your body back to the weight you had before. I might suggest you look more at how your clothes fit. You can see nearly no change on the scale, or even a small increase while your bodyfat % drops -- this would be the reverse of what we typically see in distance runners - since your lean muscle mass proportion would be increasing, it can make the bodyfat% (which is a ratio of lean muscle mass to bodyfat mass) drop. My guess is you should be noticing your clothes fit looser in those areas where we normally carry bodyfat, and possibly getting tighter where the major muscles are - e.g. quads, shoulders, arms.
