Difficulty understanding and retaining information without cramming

I've been a huge procrastinator and crammer for exams my whole life but figured I'd end the practice when I got to medical school. Despite this, there are still concepts and terms that won't really click with me until the pressure of an upcoming exam has hit me. This usually happens the weekend or week before an exam. I retain and understand information probably 50% better under this pressure than I would have if I had studied it a week before with the "I still have time to learn this" mentality. How does one fix this?