I can't get a good nights sleep?

It could be various things. What I would try first is to only use your bed for sleeping, no games, homework, texting, etc on your bed. This will allow your brain to understand that when you are in bed you are ready to sleep. Maybe you need to get more physical activity in throughout the day so you can have less energy when you go to bed. You are at an age where your body is changing a lot and that often messes with sleep patterns. If this doesn't help the topic that you should search for is insomnia, there are many tips for those suffering from this most often temporary problem.

This happens a lot to 12 year olds. It's pretty normal. Just relax and go back to sleep or eat something. Do whatever you want. You're at a stage in your life where you need to learn how to make decisions and honestly staying up isn't so bad. Have a little fun. Or just sleep lol