Did anything happen to you in the last year and a half? Did you have difficulties before this? It could be that the class isn't interesting to you. If you think it's something more serious such as a LD or AD/HD, I would see if your school has a counseling center or a learning specialist. They might be able to evaluate you. If they aren't, then they might at least be able to give you some studying techniques or tips on how to approach the class differently.