Hello Libby: This is a great question. I'm answering it from a parent's perspective who have a son in their second year as a Resident Pediatrician. . I feel that you must have "passion" in what you want to do. The passion will drive your motivation and your desire to keep moving forward. Of course, the learning material may be somewhat complex due to aggressive timelines, lots of reading & studying, etc. But, as long as you could remain focus on your goal - being smart has nothing to do with you becoming a Pediatrician. If you want something bad enough you will work hard for it. It's all about how diligent you are in achieving your goal/passion.
Here are some steps that you may find helpful on your long journey to becoming a Pediatrician:
1) Make high scores on the SAT & ACT exams
2) Select a college/university that offers at least "Biological Science" (you don't have to major in Pre-Med, Math, etc.)
3) Score well on the MCAT (Medical College Admission Test) the "first time". Retake it if necessary
4) Apply to "all" the Medical Schools of interest
5) Medical School = 4 years
5 a) Find a summer Internship Program (paid or volunteer)
5 b) DO NOT limit yourself to where you would like to get residency Matched
6) Residency = 3 to 4 years (this comes after Medical School)
6 a) Fellowship = 3 to 4 years (this is where you Specialize in, which is after Residency)
Good Luck to You!