I started my diet around two weeks ago, but gained back what I lost in week one when I was celebrating my exam results. So I've officially been dieting for a week, I've tried several times in the past but failed. Things are different this time as I've just got to the point where I'm tired and depressed of looking at myself and seeing this ugly fat girl.

I've cut down snacking and junk food and even fizzy drinks. I've also been calorie counting like mad, and been doing 20-30 minutes exercise. Except in the past two days its been more like 40mins-1hour.

Most of my exercise routine consists of 30mins cycling on an exercise bike in my living room, possibly 40 mins. And in this time I usually do around 3-5miles. Is this enough exercise to be doing? I've also been doing squats, sit ups (only managed 50 with small 5sec breaks), and I'll also be starting band exercise workout routines sometime this week. I need to roughly lose 75 pounds as a starting weight, then if I'm not happy I'll continue.

Is this good enough? If not can you give some exercise tips which I can carry out at home.

EDIT:
I've lost 7lbs this week, but I feel like I have to weigh myself all the time and even if I gain a pound I feel like I'm messing up and lose motivation. But I haven't binged at all yet.

Ate around 900 calories yesterday and burned 250cal exercising and when I weighed myself today ive put on another 2 pounds... Why is this

I'd say you aren't eating enough, personally. What are you eating, if you don't mind my asking?

How often are you weighing yourself? If you weigh daily, you're bound to see a "gain" now and then, since our bodies naturally gain and lose weight. I'd suggest once a week or less (I weigh once a week, on Wednesday mornings).

7 pounds is a great start!

I tend to miss breakfast on week days so have an early lunch of maybe a duck with veg wrapped in mooli, its around 150cal for 6 of them/Beef or tomato soup. Dinner is either a diet meal or meat/fish with some carbs and a salad. Then I have a low fat yoghurt for dessert. I drink diet coke, 7up free and water throughout the day.

Weekends will be porridge with yoghurt for breakfast.

I have to limit my diet because I don't like eggs and most fish

And I have been weighing myself daily but I've set a weigh day for every Saturday

Any exercise is good exercise. Exercise makes you feel better, stronger, gets oxygen to every corner of your body and elevates your mood and decreases your stress.

However, let's face it - it's our diet that helps us lose or gain. If you're counting calories then you should go through the trouble of calculating your BMR and stick to it http://www.myfitnesspal.com/tools/bmr-calculator. Going too much below it can cause your body to stall on weightloss, cause you to get excessively hungry which can lead to binging.

When you start a new exercise routine, your body will retain more water than usual. It may take a few weeks to adjust. Remember that the scale measures EVERYTHING - your fat, your muscle, your water, food you've eaten, etc. You only care about the fat, but that can be obscured by all the other fluctuating "stuff. " Try not to be discouraged when the scale goes up and down. Nine times out of ten, it's water weight. You'd have to eat 3500 excess calories to gain a real pound. So that 2 lbs? It's temporary, and it's not real.

900 calories is not enough to sustain you at that weight and with that much exercise. I know it's tempting to try to get there faster, but many voices of experience here will share that it doesn't work. Up your calories - even to 1500 - and you'll still lose. It'll set you up for better long-term success. Good luck!

I really think your issue is 900 calories is not enough. I have had a similar issue recently. I have a BMI of 24 and I find that during the week when I eat 1200 calories a day I lose nothing, but then I go out and let loose a bit at the weekend (so averaging about 1500 calories a day) and I lose a pound! This has happened twice in a row! So I think my body must be trying to hold onto those calories during the week! So I would DEFINITELY increase your calories.

I use an exercise bike too, but not exclusively. I put on a CD then do one song on the exercise bike, then skip for one song, then use the step for one song, etc, alternating until I've done 25 mins or one CD. I find mixing it up great and not so boring. I also swear by keeping a food diary and weighing and measuring.