Hey dude -
From what I read in your post, my best guess is that it isn't how long you study that is a problem. As me and my peers here have pointed out, how you study is likely the issue here.
I suggest you stop reading lectures. Seems like a waste of your time and it is not panning out. Maybe instead you should go to a lecture and take notes. Or take the lecture material, and put it into flash cards to get the facts in your head and test yourself. Or you could start to read the book sections your teachers base the lecture on, taking notes from the primary source.
These are just a few ideas. My suspicion is that you need to take your "passive" learning (reading), and make it "active" (note-taking, quizzing, etc.). Only you can decide if you want to take another go or not. It is your money and your time on the line, not ours.
Edit: Also - if your school has some sort of study strategy tutoring or help from their office, go do it because you need help. They will help you pass your school's coursesAs cliche' as it sounds, you have not learned how to learn yet.