Hi Charlotte,
Well done on making the choice to lose weight in the first place. Since you already use the gym perhaps you might like to try some of the resistance based machines, not only will they ramp up your total calories burnt, but building muscle will also help you to burn more calories even when at rest. Working on the legs can be particularly useful as they have the largest muscles and are therefore able to push the most weight and burn most calories. You don't need to be a gym master to use simple machines like the leg press or even do a few sets of squats, and if you are worried about putting on muscle\turning into a bodybuilder etcetera please don't be, unless you are on a very specific diet managing protein, carbohydrate and fat intakes, taking the best supplements and eating as many calories as you can then you simply wont. The truth of weight loss is all in energy balance. Calories in vs calories out. The problem with counting calories are many but the main one is that people often under report their calorie intake, their portion sizes are too large. Cereal is a major one, who actually eats 30g of cereal, thats a couple of mouthfuls. I would try something simple like adding the following into your training routine:
Bodyweight squats - 30 reps - 6 sets - 1 minute rest between sets
Leg press - 8 reps - 3 sets - 2 minute rest between sets
Leg extension - 20 reps - 1 set
Calf raise - 20 reps - 1 set
Remember to select a weight that challenges you.
And then cardio after 20/30 minutes, evidence suggests that cardio afterwards helps to reduce the soreness associated with weight training.
Hope it helps
All the best
Nat