You could try getting a calendar, and working roughly on a stone loss a month, put down how much you will weigh each month in the future as your weight goes down. Then put on the calendar birthdays and occasions. For example I'm going on holiday in a couple of weeks and at the beginning ( which is so so so hard) I just kept thinking if I stick to plan I'll be 4 stone down in my swimsuit on holiday! I also remember how heavy I was in the past and look at photos to see what I will look like. For example I remember at uni I was 13 stone, so I dug out uni photos where I was skinnier and thought, if I stick to plan I'll look like this in 3 months! Do you have an old photo that you love when you were really happy with your weight? Have a look at that and write down all the reasons why you want to lose weight, some of them can be goals, and as the days pass remind yourself what they are and achieve those goals!! Most of all, just think about how confident you will feel in your new body.
Good luck, remember no one can do this but you. You've got to find that motivation from somewhere, and it will be inside you somewhere, you've just got to find out what it is.
Just think to yourself, I've just got to make it to 3 weeks. If you can make it to 3 weeks then it will be easier, and you will have lost a load of weight! From that you can motivate yourself.
I really want you to suceed!!
xoxo