I'd amplify 1morerep's advice. There have been studies that show cardio without strength training can lower your metabolism. You want to drop the fat, but you want to avoid losing lean body mass to do so. Strength training, getting enough rest, and good nutrition (esp. a post-workout dose of simple carbs and protein) will help avoid this.
I also think that doing a "small amount" (in your words) of weight training may not be exactly the right approach. If you are doing 10 different exercises each session for multiple sets of lots of reps, then yes, you are probably overdoing things. Concentrate on quality and getting strong using the big muscle groups in complex exercises that pull several muscle groups into action (squats, deadlifts, bench, rows, military, chins, dips). One program to try is based on Mark Rippetoe's beginning strength program. There are some variations out there, but basically you concentrate on good form, low rep sets (3 sets of 5 or 5 of 5), and a few of the above exercises each work out. You start off fairly light to train your form, adding weight each session. You do not work to failure. Squats are in each session. The others alternate every other session. My experience is that you see some good progress in the first month, but really start cranking in the second and third. I also was able to get a good workout that saw marked strength gains, some muscle growth, and allowed me to still hit the cardio.
You don't say how flexible your schedule is, but if you can try breaking up your cardio and strength workouts. You can do this either by splitting them into AM cardio and PM weight training, or separate cardio and strength days. I do the latter, with a light 10 min. cardio warm up, lifting (do warm up sets as well), then follow it with light 12-15 minute cardio and a 5 min. cardio cool down. This burns several hundred calories from cardio on my strength days, and still doesn't kill me. I then have 3 more intense cardio days with no weights (I do intervals one session, high intensity but short steady state in another, and long, low intensity in the last). I start the week with my highest intensity cardio day, so it isn't hampering recovery from a strength session. Ocassionally, my body says slow down and I drop a post strength training cardio altogether and do extra stretching and muscle release work on rollers). This has worked well in the past when I let myself go and needed to start from a fairly low state of conditioning. You do need to make sure that you get extra sleep, take your fish oil, and be good about pre & post workout meals and getting some good protein before bed to make sure you recover.
If your schedule isn't so flexible to do this much or your body tells you it's too much, don't get too hung up as this is for the long haul, and if you keep it up, your conditioning will allow you to do more. Good luck!