One thing that you can do to make sure that you stay on track with your diet and exercise plan, is to not make it too strict. When you go all or nothing and you go for weeks on a super strict diet with no treats allowed, it is like a pressure cooker. Your cravings for treats heaps up and up, until one day the pressure are too much and you binge all out, just because you denied yourself treats.
So even though I am on strict diets, I still allow myself the occasional treat, that way I limit the chance of falling off track. If you are craving chocolate, have one or two small blocks. Just make sure that you don't have it too often and when you want a treat that you only have a little bit of it.
Here are a few things that always motivates me, try them, they might also work for you: set smart goals,write down your reasons for wanting to lose weight and stick it up somewhere you can see it, you can also cut out a pic of how you want to look like and stick it up next to your reasons, and it also help me to have a mantra like "I can and will lose weight for myself", or whatever motivates you.
If you have the money, it can help you a great deal to consult a nutritionist/dietitian. I recently saw one and she helped me a great deal to lose weight.
If you don't like exercise, try doing fun activities instead where you can still burn off some calories. Some of my favorite non-exercise activities includes: hiking, ballroom dance classes and tennis. You can also try belly dancing or pole dancing lessons, or take up a new sport.
Good luck and always believe in yourself!