How can I lose around 40 pounds?

I’m about 40 pounds overweight, I have very very little will power to do this stuff. =P, My whole family is overweight and we all start to do diets but then gradually get off of it. I know eat small and stay around 2,000 calories and drink water and exersize. Everyone knows that. I just need to do it with someone, none of my friends or overweight so I can’t ask them and my mom always does different diets than I do and she won’t get up and do anything with me. So mabye someone on here can do it with me? I just need to know what kinds of food I need to eat. I know yogurt in morning chicken or salad in lunch and somthing small for dinner but only have little snacks. I need someone to do it with so I might get some willpower to go on. How long will it take to lose 40 pounds healthy and make it stay off? We have a lot of junkfood in the house and I try to not eat it but then everyone else does… so I have to >.> Please help! Thanks