I gained a lot of weight when pregnant due to health problems that affected my mobility and constant hunger that would make me really sick if I didn't eat. I had 4 and a half stone to lose by the time baby was a couple of months. All fat tbh :-) It's all gone now. Here's what worked for me;
The hardest thing is getting started. Eating first;
Only buy healthy foods that you intend to eat, no junk at all. If it's not there you can't give in to temptation!
Eat a lot of protein, it fills you up.
Eat plain for the first couple of months. Eat the same breakfast every day and don't vary meals too much, that way you're not thinking of food all the time and the health food just becomes 'normal', even on auto pilot you are reaching for it. That's the type of attitude you need to develop because your current instinct is to grab the junk that has become 'normal' for you ifswim? I'm convinced that people put on weight due to dieting because on a diet you are always thinking of food.
Use small side plates for your much smaller food portions, that way you can still fill your plate but not too much.
Drink a glass of water before eating and another one during your meal.
Now the exercise part. If you can't (or don't want to) join a gym, you can buy exercise dvds, free weights and exercise machines if you want, you can get them at relatively cheap prices, look into whatever you're interested in before buying, they can be a great investment.
You need to build muscle because it burns fat by speeding up your metabolism, it also tones your body making you look slimmer and improves your shape. The best thing you can do for that is weight training, Pilates is also good (both would be great). Cardio is also important for your health and for burning calories, brisk walking, running, cycling (if your outdoorsy) exercise bike, cross trainer, treadmill (if your not). Aim to do 40 mins - one hour of weights/Pilates and 40 mins - one hour of your chosen cardio a day. (obviously you have to build up to that, not on your first day!) six days a week.
It is a lot of hard work to lose the weight but it's worth it for the health benefits and of course the added confidence you will have by looking your best and feeling great!... Have a vision in your head of yourself being healthy, energetic and slim and keep that in your head when you're preparing food/eating and exercising to keep in mind what you're aiming for.
Hope this has been some help to you, all the best with your weight loss 