If you're doing pretty low intensity workouts I take back a little bit of what I said... like your weight training sounds like a really good level to start at, and if you're not doing insane sweat-till-you-drop aerobics every time, and you're not feeling overly tired, then I'm sure you're ok. Plus if you're enjoying it I wouldn't want to tell you to stop!!
Just watch for signs of overtraining - like increased tiredness, slower recovery time after exercise (you feel sorer longer than before), decreased appetite. Stuff like that.
I'd also chime in with Casey and recommend counting calories. It can sometimes be surprising how much or how little calories we get each day. Plus if you know how much you're eating and burning you can have a better idea of why you are/aren't losing weight.
FitDay.com is a free site that makes this really easy. LOL people are going to start thinking I'm the fitday nazi or something or that I work for them! Honestly I just love this site because you don't have to do any math! haha... I use it myself to count calories of food and exercise and it's really easy. You can also keep a journal. Ok enough with the plug... seriously, they're not paying me I swear!