You can do it! But just remember it may take time. I too, have been overweight most my life and it is frustrating. I started at 190lbs but now Im at 180! It did take though 2 months of going up and down. I still will wake up some days and be 182 and then 180.
Tips that I have discovered that really helped me was not to weigh myself for almost 1 full month when I first started fatsecret. I try to not eat 3 to 4 hours before bed. And I started out slow with exercise and increase slowly over time. Im one of those people whose weight increases when I start to exercise because muscle weighs more than fat. So if you start to exercise don't become discouraged if the scale doesn't show a ton of weight lose. I also measure myself for better accuracy.
Oh and one more thing, do not trust the BMI! It does not take into account ethnicity or bone structure. Often times, with the BMI, people who are from an Asian background will come across as under weight and big football players are in sever obesity level 2.
Welcome to fatsecret and I hope it works for you! My brother lost alot of weight, that is why i joined fatsecret because it worked so well for him. He was around 290 (I believe) and now he is 250! Just don't give up and keep trying!