You'll have to pick something, slow down at a pace you can handle, or jettison yourself through graduation with terrible grades. As a former premed courses tutor, I heard things like "not having time", and "not being as smart as everyone else" all the time, but this was seldom ever true.
My advice:
1. Get a tutor, now. But, do prepare for tutor sessions, a lot of people just "show up" to tutoring sessions, this is a waste of time for both parties and probably the number one reason why most people don't get much out of tutoring sessions. Your school likely has 1 on 1 tutoring as well, they are likely part of your student association fees. Try to get a 1 on 1 tutor if possible, so they can audit how you study, your HW habits etc.
2. Prioritize your schedule. Are you paying for school yourself? If not, then you have plenty of time to study -- case closed. If you are working to pay for your own education, then you may have to pare some of your costs with more grants or loans so you can be what you're supposed to be, a full time student. Take being a premed/student as a job, a career.
3. Get counseling for free at your school, being a crappy mood never helps grades.
4. Stop thinking about graduating "on time", unless you're paying out of pocket and are exceeding your budget "on time" and "medical education" have little to no correlation. If you want to rush out, you'll either just end up going to school again for a post bacc, or masters depending on the rest of your application. So, if the purpose is to rush out of college into medical school, then rushing out of college wouldn't be the smartest thing to do given your circumstances. Slow down, take your time, and do it right, or else end up doing it over again...or worse.
This is not an intelligence problem, this is a learning how to be a college student problem that we all go through (hopefully).