shedding fat in abdomen area?

I want to lose about 7 inches off my abdomen area in a month, which I think is a reasonable goal… right now I am doing 30 min on an elliptical (but I do it very fast, high heart rate of 160 bpm – is that too much?); then I do crunches, situps on a medicine ball. I do this daily.

Any other suggestions? Good workouts to add in? I want to lose the chub around the middle and introduce a flat tummy, doesn’t have to be toned, just flat (no sticking out, bloatyness). I just got sick and tired of not taking care of myself.

So any good cardio suggestions? I have a gym membership so I have access to all the machines/tracks/everything I can handle, am just lost and don’t want to spend 150 dollars on the trainer session the gym offers
I’m 5’6, 140 lb, so I’ll probably have to lose about 10+ lb on top of it… but I’ve really cleaned up my diet and I’m exercising… is it doable in a month?