Thanks for reaching out to us tonight! It sounds like you are going through a rough time. Its great that you are trying so hard to finish 12th grade!! Keep up that determination! A lot of people struggle with school, especially tougher classes like Economics and Government. You mentioned you tried getting help. Have you tried getting a tutor?
Maybe one-on-one help would be helpful to you. Otherwise, a lot of kids find study groups to be effective too. Find other kids that are in your class and see if they want to get together after school a couple times a week and study. This will help hold you accountable and it can also be beneficial to see class notes and discussion from other people's perspectives. If nothing else, you can also go to the teacher and ask them if there is any extra credit opportunities available.
Talk to him/her calmly and respectfully and let them know (if you haven't already) that the class is difficult for you and you need a little bit of extra help to graduate. Most likely, your teachers want you to succeed and pass high school, so they will try to help you wherever possible. Its worth a shot! Good luck and hang in there! You can definitely do it!