Whats the best birth control to not gain weight and prevent pregnancy in the near future?

The one you use. : Best form of birth control is the one that you will consistently use and use correctly. If the pill is freq missed then another method such as a nuvaring, implanon, or iud may be better. Most data indicates that weight gain is not generally an issue.

IUD/Implant: Regardless of your age, blood pressure, family history, or reactions to other birth control, the most effective and safest methods of birth control are long-acting progestin-only methods, such as the implant or the hormonal IUD, which decrease rates of endometrial cancer and decrease bleeding. They're safe, reversible, and don't affect weight gain/mood. They're almost as good as getting sterilized