Can I get somewhere in life?

I currently have a ulative GPA of 2.534. I don't know why, but I have alot of trouble getting decent grades. I'm not stupid, but I'm just not good at school. Right now I'll be lucky to finish off my junior school year with a 2.4 for the semester which should keep me at 2.5 ulative. I want to study exercise science, but I have scored poorly in all sciences-I currently have a D in chemistry. Will it make a difference if I go to a lesser ranking college such as Western Illinois University instead of a college with higher standards? I have this impending doom feeling on my shoulders, like once highschool's over its the end of the line for me. Can anybody relate?