Well, you REALLY have to work on your reading comprehension skills. Spend more time reading, esp materials that are difficult for you. Read everything, science articles, fiction books, whatever. Spend more time per day reading. If you improve reading comp, usually your reading pace increases dramatically.
Your reading and critical thinking abilities will naturally improve in college.
I tell you this - if you bust A's in all your science courses and non-science courses, you will be ok for the mcat and med school admissions. But to do this, you will have to work really hard and have mucho self-discipline.
If you struggle all through your coursework, avg a C+, B-, etc. , the mcat will be one in a plethora of problems for you
So, in sum, don't worry about the mcat just yet. Register for premed courses and rip them apart.