Rachel, it sounds as if you have been waiting a long time. When I was 12, then when I was 16, I repainted my own room. I found a lot of satisfaction in being able to do it on my own. Since you seem to have hit a brick wall here, although I am not suggesting you take on the entire project alone, I am going to throw out an idea for you to think about & see if you can make it work.
Find a day that your Dad is just hanging around the house. Start moving out all the furniture that you can move by yourself. Don't worry about the stuff that is attached to the wall or too big to move. Start working on an area of the wall that you can clear. While you are moving things out of the room, and setting things up, make as much noise as you can. Set up the paint, protect the areas that need protecting (see the link I have included below) make sure you have a dropcloth or an old towel to keep from making a mess, and just start painting the areas that you can. If your Dad is anything like mine was, when he sees you really trying and you are messing up the paint job a bit, he is going to just jump right in there and take over. Keep working with him and allow him teach you how to do everything for yourself. It will be a great way for you two to spend some quality time. When he starts in, give him a big Thank You and a hug. Make sure you thank him again when it is completed.
Here is a link to help you learn how to paint a room. Please read it & you may want to print it out to use as a guide
How to Paint a Room | Step-by-Step | Painting | This Old House - Introduction
