I was just like you especially throughout my high school. In college, I did three things.
1) Get a study group. Do your homework with your friends. Not only does it help you form social supports in classrooms in case you need help from them, but also these friends contact you for meeting up and doing homework. You might be less distracted with friends doing homework around you.
Depending on what type of friends you get, though, it will be even more distracting because they might be talking about TV shows all the time while doing microbio homework. Find other pre-meds or those with good work ethic to do homework together, if that's the case. These friends can give you reminders for homework or deadlines. They can also force you to do homework in certain time.
2) If you get too distracted, do other ECs like staying up till 3 am in research lab doing WB or IHC. Force yourself to the extreme and test your time managements. Tell yourself: "If I cannot handle this workload, I cannot handle medical school." With more limited spare time to do homework, you might be more focused because otherwise you won't be able to finish them promptly. Don't let anyone set the limit on you. Just because people around you are taking a certain amount of classes, it doesn't mean you should as well. Take more (fun) classes, do more research, and do more meaningful ECs that you enjoy.
Start those ECs correctly this semester (especially research) so that you will enjoy doing them for 3+ years by the time you start your application.
3) Think about how everything integrates together. You won't be able to integrate things until junior year or even after graduation, but it is important to start thinking about it early. How does stuff you learn in physics relate at all to stuff in bio? How does stuff you learn in economics class relate to stuff you learn in human behaviors? How does everything you are interested in and passionate about relate at all to where you are coming from and what you want to accomplish in your life?
Knowledge integration is crucial not just in medical school, but also in life. For example, there is a huge difference between people who see obesity as simply a lack of exercise and poor dietary habits and other people who see obesity as a complex illness incorporating neurological dysfunction, poverty, infrastructures, agribusiness policies and motives for profit, and so on. There is a huge difference between people who know what they want to accomplish in life and other people who just want to get into medical school.
In doing so, hopefully you will be more driven with clear directions.