Hi Amber, firstly, I'm sorry about your friends treating you that way but about your parents I think that they say it for your well being because I have seen parents do that. If you don't like it, you can talk to them about it and they would understand. Maybe your parents don't realize how it hurts you when they judge you while your eating a sandwich or something similar? Talk to them and I'm sure they will support you.
I was never overweight, but I had a bit of a tummy when I was 11 or 12 lol, and I got rid of my tummy just by being active everyday with basic physical activities and I only sat down in one place to study or read the Bible or to read some other books. Now I workout each day to remain fit. Here's my advice - First get a strong relationship with God, I'm not sure about your relationship with Him. Then tell God your problems, about what your friends tell you and about your parents and about your weight. Dont get me wrong, don't just make your relationship stronger with God only to lose weight. Show God how much you love him and spend time with him more than anything else.
Now, you need to control the calorie intake. I would suggest that you split your meals. Instead of three meals a day, split them to 5 or 6 meals, keep a time period of 2-3 hours between each meal. Each meal should consist of about 200-300 calories depending upon your daily activities. Exercises should be done as well, cardio exercises are really good and easy. Fitness Blender is a good channel on youtube that can help you with the workouts. Proteins, carbohydrates and fats should be taken in at equal proportion for each meals. Meat, vegetables, organic food, fruits, green tea, citrus fruits should be taken and avoid junk foods or limit them to once a week. Celery can help you lose a lot of weight because your body requires more energy than what the celery provides to digest the celery, so your body uses the stored fat to fulfill those energy needs. Celery isn't delicious, so I would suggest to have some low fat sauce with it.
Don't be sad or depressed about what others tell you. Jesus loves you, we all do love you too. I won't care what your weight is, your still an amazing person. Many overweight women have got over it Amber, you being a child of God can definitely do it as well.
Feel free to pm me if you need any help, welcome to CC and Gold bless you!