Based on your stated goal, "to lose weight", you have to do one thing, expend more calories than you take in. It really doesn't matter what you do, eat, say, wear, or feel, that is the real and only answer.
But to put it in your context, what you want to do is a two things, 1) change the ratio of calories in to calories out by making tweaks to your diet and the way you eat, and 2) make changes to your routine, and thus your body, that will tip the scales in favor of weight loss.
The diet and nutrition variable can't be discounted! A calorie is a calorie, and you must alter the ratio of calories in and calories out in order to lose weight. Start small! Drop a coke here and there, try a low fat alternative for that ice cream. Start reducing the size of your portions a little bit. Eat more often, snacking and grazing (on healthy food!) rather than having a few large, heavy meals. Make small but constant and consistent changes to your diet that move you towards more efficient use of your calories. Small changes here and there add up over time, so start small and don't rush this step, or you'll find it difficult to adhere to.
As to your workout, you will burn more calories over time by consistently doing resistance training than you will by consistently doing aerobics. Most people will tell you that you burn more calories during a run than you will spending the same amount of time pushing iron. This is true. But it's not the whole story.
You get most of the weight-loss effect of aerobics during the exercise. When you stop, your metabolism quickly returns to normal levels. But with consistent and frequent resistance training (3-4 times a week), you are tearing your body down, literally, so that it must repair itself. This requires a lot of energy - a calorie is nothing more than energy. The more muscle you need to repair, the more calories your body will consume doing so. This effect lasts for hours after your workout is complete. You don't tear down much muscle during aerobic activity, so your body recovers from it much more quickly.
Definitely alter your routine by adding some resistance training. But don't stop the boxing, a balanced combination of the two is your best approach. You actually need both weight training and aerobics to lose the most weight in the shortest period of time.
And great job on the boxing! I tried it for a week, and found a whole new respect for how hard it really is!