should i get braces im 15?!

Well, how do you smile? If you smile showing your bottom teeth, than it might be helpful to get braces again. Since it's only your bottom teeth and for most people, when they smile, you only see the top row, so it won't matter. It depends though, if you feel like you'll more be confident then go ahead.
My teeth were only slightly crooked and I didn't need braces, but I did end up getting them because I wanted straighter teeth, and now i smile with a lot more confidence.

there not that expensive if you go to a dental school, where people are learning how to do that kind of stuff, my friend did that and got them done for less than a regular dentist (because the people where inexperienced), they turned out ok!!

im sure your parents don't want to pay again. no matter how much it is. put your retainers in for a few nights and it will most likely straiten them up.

Well braces are expensive. Its up to you but they are around 5 grand.