Weight loss

So I'm sort of a big girl. I get teased by family and my love's family. While he does tell them something it doesn't mean I don't want to prove them wrong. So I started counting calories and got a job at a warehouse so that I'm constantly moving. The first 3 weeks I lost 10 lbs but now I've stopped losing weight and it's been 3 months already. My best friend and I picked a dress that really will show my success and I need to wear that dress and I also want to be healthy. I need help please someone tell me what to do.