Birth control information

I just schedule an appointment with my gyno to be put on the pill. I’ve never taken birth control so I’m a bit nervous. I’ve heard it can cause you to gain a ton of weight, I don’t want that because I’m already very insecure with how much I weigh.

Is it 100% effective? I don’t want to use condoms anymore, but being the anxious person I am, I feel like I can still get pregnant even if I follow the instructions carefully. And will I gain a lot of weight? Or are the birth controls different from each other depending on which one you take?

I’m also pretty sure I have PCOS. I have hair on my chin and my neck, my periods are irregular and hurt like crazy. Very heavy too. I need to get that diagnosed, so any way I will probably need to be put on birth control.