Welcome to the board.
I absolutely do think you should talk to a doctor about this. It's one thing if you are seeking drugs to boost grades, or let you work all night. It's another thing entirely to try and try to sit down and get work done, and then just not get it done all too often.
You experiences do sound a lot like those of ADD people. What to do? Dont be "Hey, get me a script for some ritalin." Just explain the problem, and let the doc propose a solution. I'll tell you this--if it is ADD, drugs might be very helpful, but they won't be the whole answer. They allow you to study and concentrate, but then you have to learn how, the way other people did back in grade school!
Regarding price: some are pretty expensive, but if you mention that price is a concern, the doctor may be able to prescribe older drugs or generics that are reasonably affordable.
Oh, and if you do decide to take meds, you may have to try a few before you find one that works without intolerable side effects. Or, you may get lucky on your first try.
Good luck, and do pursue this before you can fall too far behind in college.