[Tigerlily.]

1. Will the pill help? Will it make me gain weight? Are there any negative side effects I should consider?

It most likely would help, but the pill has different affects on different people, if you tell your doctor the main reason is for your period, they are more likely to prescribe you one with a higher rate of helping periods than if it were just for birth control. And again side effects vary for everyone, you may or may not gain weight, we can't say for sure if you will or won't, even if we did know what brand you would be on.

2. Should I approach my mom or wait until October when I can drive myself to Planned Parenthood privately?

That is completely up to you, but if you are worried about your mom knowing, since it's mainly for your period, I'd say it can wait. But remember, it takes about a month for the pill to become effective as a birth control, and anywhere from a couple weeks to a couple months for the pill to affect your periods in a positive way if it will depending on the brand.

3. If I should approach my mom, how? I don't want an awkward conversation. I wish she would just see me as an adult and I don't feel I can talk to her about anything like this. :/

Just sit her down and explain how awful the cramps and flow of your period are, and that you would like to try birth control pills to help with it, assuming you do decide to talk to her. You just have to be upfront about the reason, and don't give her a reason to think you're lying, I'm sure she's noticed the size/flow amount on your tampons if she's ever bought them for you.