First, I strongly recommend that you search the recruiting website, this site, and talk to a recruiter.
Second, I am not an expert, I'm just an ROTP student who has read a lot on this site (recall that this section can only be posted in by people with less than 250 posts).
I am not aware of a program to take a high school graduate all the way through to practicing doctor. There is MOTP (medical officer training plan), which is for candidates accepted into a Canadian medical school. It pays your tuition, books, salary, etc. After your residency, you would owe four years of service, if you want to specialize, it increases the time you owe.
For your undergrad, you have three options: on your own dime, with the reserves, or ROTP. With the reserves, you work part-time (one night a week and one weekend a month, I believe, possibly more for initial training, with the possibility of summer employment) in some other trade. You can get 2000$/year to a total of 8000$ for university, so long as you are in the reserves while you are going to school. Then you would have to get accepted to medical school and MOTP and transfer (somehow) to Reg force (I've heard it can be complicated to do). The last option is probably the most complicated. You can apply for ROTP for some other trade. ROTP will pay tuition, salary, books, etc., and you do your trade training in the summers. This will incur four years of owed time (if you start in first year). From then I'm not sure if you would have to serve out your owed time in that trade or if you could try to apply for MOTP right away (there is something like MOTP for serving members, I don't know if it has the same name). This is all presuming everything goes according to plan, of course.
If you have any intention of seriously doing this, I highly recommend you not rely on the advice of random strangers on the internet and GO TALK TO A RECRUITER. Search the forum too, I'm sure this has been covered somewhere. But if you are wanting to get into either the reserves or ROTP, get on that, the deadlines are coming up for ROTP (you might not make them in time at this point). The availability of jobs right now doesn't seem to be what it once was!