I need to lose weight ASAP

My goal for 2018 is to lose weight. Back story is at age 15 before I got pregnant with my first child I weighed 125 and my height was 4’11..I gained about 35 pounds during pregnancy so I ended up weighing 145/146 and than a year later I got on birth control and I still weighed 146/147 still 4’11/5’0 at 17 years old. 3 and a half years later I’m now 21 and I just got my birth control removed in November I weigh 187. I did eat a lot of fast foods and hardly exercised and even when I was working and my working involved a lot of walking and standing for a period of time I still felt like it was impossible to lose weight. I want to weigh at least 140 that woud even be progress compared to 187. I don’t want to reach 200 at 5’0 and being 21 so please any apps you use , diet plans , cardio workout plans you got or tips let me know. 😩